All countries

TravelSim
TravelSim is one of the oldest companies to have launched an international prepaid card, using an Estonian (+372) number. It has voice and text service in about 190 countries and proved to be quite reliable.

The only problem has been its very high cost for data. If you travel a lot and always go to different countries it can be much more comfortable to use only one prepaid number which can be used (almost) worldwide. But this has an extra price.

In 2014 they lowered some data prices and introduced the TravelSim Data Card. The following prices only apply to their data and not the voice card. Though the data SIM has voice too, but at unfavourable prices.

Startup price and availability
The TravelSim Data is only available online on their website with worldwide free shipping. It costs 25 EUR with 25 EUR credit and comes as micro-, mini- or nano-SIM. It can be reloaded by international credit cards on your TravelSim Profile online and stays vaild for 2 years after the last top up.

Validity
Unlike voice and text, data is only available in about 100 countries and 2G and 3G only. The rates range from crazy 20.00 EUR to 0.19 EUR per MB depending on the country. The price model is split into 2 schemes: a pay-as-you-go rate and package rates.

Pay-as-you-go-rate
It's the default rate when no pack is booked and the only rate for some countries. Rates are charged in 1 KB or 10 KB increments and the most important countries are:
 * 0.19 EUR per MB: in the entire EU, Norway, Russia, Hong Kong
 * 0.39 EUR per MB: in the rest of Europe, Australia, Egypt, India, Israel, Korea, South Africa, Turkey, Thailand, Taiwan, USA, Canada
 * 0.50 EUR per MB: China
 * 0.75 EUR per MB: in Indonesia, Malaysia
 * 1 EUR per MB: Brazil, Japan
 * 8 EUR per MB: Moldova
 * 20 EUR per MB: a lot of countries in Latin America, Africa and Asia,
 * see new price list in pdf

Data packages
Furthermore, they now offer the following data packs to be booked on the personal portal of the SIM (navigation to that is free): Be aware that billing is in disadvantageous 100 KB increments. The package prices listed above only apply to the following countries: the complete EU and Albania, Azerbaijan, Australia, Belarus, Egypt, Hong Kong, Iceland, India, Indonesia, Israel, Moldova, New Zealand, Norway, Russia, South Africa, South Korea, Switzerland, Thailand, Taiwan, Turkey, Ukraine, UAE, USA. The other countries are only available on pay-as-you-go.

Data traffic from the most countries outside the EU is counted twice (2x). So the rate in packages for EU countries is about 0.10 EUR per MB, the other countries mentioned above about 0.20 EUR per MB. Thus the packages are about half of the price of the Pay-as-you-go rate for most destinations.

More Info
The rates are surely above the prices of average national data SIM cards. But there is hardly one product comparable on the market. Other international roaming cards like XXSIM and Maxroam don't offer so low prices for worldwide data, that's why they are out of the list. It depends on how much you are willing to pay extra for an almost worldwide solution. Always compare the TravelSim rates with the roaming rates of other mobile providers.
 * APN: send.ee
 * Username: number of your Travelsim: 3725......
 * Website: www.travelsim.com

OneSimCard
On the other side of the Atlantic OneSimCard by Belmont Telecom Inc. offers a very similar product. Its "data & roam" SIM works in 160+ countries, is also based on an Estonian number (+372) which is added by a US or Canadian number and has essentially the same rates like TravelSIM.

The main difference is the underlying currency of US$ instead of Euro. The SIM costs $29.95 with free shipping in the US and the tariff table is identical to TravelSIM: The PAYG rate of 0.19€ is $0.25,  0.39€ is $0.50 going up to 20€ or $25. They also sell totally the same data packages for the equivalent rates in US$. Although data of some countries are not counted twice in the packages like with TravelSIM, they simply cut in half the allowances of the (2x) countries, which is the same in the end. For more info see TravelSIM above or check their website. If you live in America, it might be the closer choice for you to get the same SIM plan.
 * APN: apn (no joke, but only for the OneSimCard data & roam)
 * Website: http://www.onesimcard.com

XXSim
Like TravelSim XXSim is a reliable international SIM card based on an Estonian (+372) number which has been around for years. In fact, both products use the same platform. Voice is available in about 190 countries and data in a few less. While TravelSim has issued a data card, XXSim has not (yet). XXSim offers the exact same data prices given above at the pay-as-you-go-rate, but they don't offer any packages though.

That's why XXSim can't be recommened. First you pay the premium of an international SIM card, but you don't get the discounts of TravelSim. Charging 0.19 EUR per MB within the EU, you are almost at the price cap for any SIM card sold in the EU with roaming data. So for many users the roaming option of your home carrier is the more convenient choice at the same price, while TravelSim is the cheaper alternative if you want to buy an international card.

Piranha Mobile
Piranha is an international SIM card coming with an US (+1) and an UK (+44) mobile number. It offers prices below TravelSIM at the cost of less reliability and comfort.

Start-up price and availability
The starter pack is available only online as mini-, micro- or nano-card in three denominations with free international shipping: Top ups can be made online with credit card or PayPal. Auto top-up can be linked to a credit card.
 * SIM card with 5 GBP credit: 12 GBP
 * SIM card with 30 GBP credit: 35 GBP
 * SIM card with 50 GBP credit: 50 GBP

Generally, they offer good rates on voice, text and data, but the rates are as complicated as the technical settings. Most calls are made through the callback procedure. In tests, the card proved not to be very reliable: calls were dropped and texts were lost. Many users are confused with its handling.

Data rates
For data, they offer roaming in about 140 countries. It is billed in 50 KB increments. Rates differ even in the same country, depending on which local roaming network you are on. Some price examples: Because of different rates for different providers in the same country, be sure to pick the cheapest first and disable automatic network selection, so your device can't switch the roaming networks. Furthermore, Piranha mobile allows you to make calls through VoIP if you install their VoIP app or have a VoIP-router and Wifi connection.
 * 0.07 € - 0.13 €/MB: all EU and EEA states
 * 0.08 €/MB: USA (T-Mobile)
 * 0.13 €/MB: Australia (Optus), Canada (Rogers), Israel (Orange), Russia (Megafon, Beeline), Turkey (Vodafone), Japan (Softbank), Thailand (AIS), S.Korea (KT), South Africa (Vodacom), Switzerland (Orange, Swisscom)
 * 0.26 €/MB: Brazil (TIM; Vivo), India (Reliance, Aircel), Indonesia (Indosat), Mexico (Movistar)
 * 0.39 €/MB: China (Unicom)
 * 0.65 €/MB: UAE (du), Egypt (mobinil)

More info

 * APN: openroamer.com
 * Website: www.piranha-mobile.com
 * Extensive discussion here

Truephone
Truephone is a British provider offering a multi-SIM card for discounted calls, text and data abroad. Here only their prepaid product is shown. Multi-SIM means that you can buy their SIM card and add some other countries with local numbers on it.

Right now for prepaid, you can buy a UK, Australian and US SIM card or combine these countries as home countries on your multi-SIM. Other countries are planned for 2015. The local number will be shown to the caller. Roaming is possible in "over 200 countries", although the UN lists only 193. They base their roaming largely on a cooperation with different Vodafone networks.

Startup price and availability
Their SIM card needs to be ordered online here for 19.99 GBP/EUR or 29.99 AUD/USD coming with 10 GBP/EUR or 15 AUD/USD credit. Each additional home country can be added for 5 GBP/EUR or 8 AUD/USD. All sizes of SIM cards are available and worldwide shipping is free. Credit can be added of 10, 20, 30 or 50 GBP/EUR or by auto top-up linked to a credit card. The SIM card must be activated and an account created online here.

Data rates
All voice calls per min, texts and data per MB is 0.07 EUR / 0.06 GBP in the "Truephone zone". Roaming is mostly on Vodafone networks where available. These data prices are charged in EUR to give some examples: More prices here. Speed depends on local availability, though 4G/LTE is not supported. They offer more prices and even data packages with postpaid products aimed at business travellers.
 * 0.07 EUR per MB: Truephone Zone: UK, Australia, USA, Germany, Netherlands, Hong Kong, Poland, Spain
 * 0.18 EUR per MB: all other EU and EEA countries
 * 1.80 EUR per MB: Switzerland
 * 2.20 EUR per MB: South Africa, India, Thailand, China, Japan, Indonesia, New Zealand
 * 3.60 EUR per MB: Canada, Mexico
 * 7.20 EUR per MB: Argentina, Brazil, Egypt, Turkey, UAE, Russia

Validity
In the event that you do not use the SIM card for any continuous period of 180 days, they reserve the right to invalidate the SIM card and/or call balance components and cancel your account without prior notice and without any refund, repayment or compensation.

More Info

 * APN: truephone.com
 * They offer a Truephone app which only provides free international calls through VoIP over WIFI.
 * Website:http://www.truphone.com/row/consumer/sim/

KnowRoaming
KnowRoaming is a Canadian start-up with a new approach: They provide a "SIM sticker" which has to be applied to your home SIM. Thus, all calls, texts and data outside of your home market are diverted through the KnowRoaming SIM addon. Their sticker intercepts electrical signals before they go to the regular SIM. If you're in your "home" country it passes everything through. Otherwise it "takes over" and functions as a second SIM. They claim that this sticker will fit over regular, micro and nano SIMs.

As they just have started no feedback or reviews about the reliability and practicability of this system can be given right now. What they don't say is that Apple denies all warranty, if the SIM-card-holder is damaged by manipulated SIM-cards.

Startup price and availability
The SIM sticker is only available online on http://www.knowroaming.com with worldwide free shipping. It costs 29.99 $ with 15 $ credit and comes with an applicator for micro-, mini- or nano-SIM. The SIM addon can only be managed and reloaded by their app available on Android, iOS and Windows Phone.

Validity
Their SIM card will be terminated after 15 months of inactivity. Data is available in about 80 countries and 2G and 3G only. The data rates range from 0.15 $ to 0.65 $ per MB depending on the country. Like TravelSIM, the price model is split into 2 schemes: a pay-as-you-go rate and a package rate.

Pay-as-you-go-rate
It's the default rate and the only rate for some countries. Here are some examples:
 * $0.11 per MB: USA
 * $0.15 per MB: all countries of the EU and EEA, Australia, Singapore, South Africa, South Korea, Switzerland, Turkey

see full prices here
 * $0.20 per MB: Hong Kong, India, Israel
 * $0.25 per MB: Mexico
 * $0.30 per MB: Argentina, Russia,, Thailand
 * $0.33 per MB: Japan
 * $0.45 per MB: Canada
 * $0.50 per MB: Brazil, China
 * $0.65 per MB: UAE

Data packages
Furthermore, they offer the following data pack to be booked by app: In their T&Cs they state a Fair Use Policy, that they can throttle speed to 258 kbps after having reached only 250 MB per day.
 * "Unlimited" data for $7.99 per day. This pack is only vaild in all EU countries, Albania, Armenia, Island, Macedonia, Russia, Serbia, Switzerland, Ukraine, Mexico, USA, Hong Kong, Israel, Japan, Singapore, Thailand, South Korea, Kazakhstan, Ghana, South Africa, Australia, New Zealand and a few more

More info

 * Website: http://www.knowroaming.com
 * Forum discussion here

ChatSIM
ChatSIM, formerly known as WhatSIM, is the first international roaming SIM card aimed at social messenger users only. This Estonian-based SIM by the Italian MVNO Zeromobile roams in 400 networks of around 150 countries. It supports all messengers like Telegram, WhatsApp, Facebook Messenger, WeChat, Skype, Viber, LINE, Google Hangouts, iMessage, QQ and most other instant messaging apps.

The SIM card needs to be ordered online on their website. They charge 10€ for the SIM and at least 5€ for shipping. All three SIM sizes are available. When you get the SIM, it needs to be activated online. For the 10€ charge, you can chat for one year in all countries. But this refers only to text and emoticons. A FUP of 3,750 to 25,000 text messenges depending on country is enforced too.

For multimedia contents like photos, video or audio, a price scheme based on credits and zones is in place. To send multimedia messenges, you need to top up at least 5€ as well as for all other internet browsing. The zoning starts at 50 credits (= 0.25 €) per MB in the EU which is even above the EU data cap. It goes up to 750 (= 3.75 €) credits per MB in exotic countries. All multimedia content and surfing other than text messenging are charged accordingly. VoIP or other calls through the messengers are possible, but billed likewise. Voice calls and SMS are not supported.

Reloads are by credit card on their website. It will not expire, as long as you use it once within 12 months and top up 10€ every year. You need to switch off data traffic on all mobile apps on your device as long as you don't add extra credit because your SIM will blocked, if anything else but text messenging is detected and you don't have credits. So better think twice about this SIM even if you are a chat fanatic.
 * APN: send.ee /or/ apn
 * Username: your phone number: 372.........
 * Website: http://www.chatsim.com

Droam
Droam is a Dutch company which offers a Mifi device for rent with global data roaming.

MiFi
A MiFi is a pocketsize wireless router that acts as mobile hotspot. Connected to an internet provider, it can provide access to the internet for a number of devices at the same time by WIFI. To this Mifi router up to 5 mobile devices can be linked simultanously.

Rates
For countries a time (1)  and a volume (2) rate apply together:

(1) Time: From 1.50 EUR per day in the EU to 5 EUR overseas

(2) Volume: Droam has coverage in 160 countries, with country-specific prices: list

Shipping
Shippings free in the Netherlands when sent using regular mail. FedEx "priority" shipping is available to and from many countries, including the Netherlands. FedEx Prices range between 14 € and 60 € one-way.

Security Deposit
150 € security deposit for Mifi device, returned within 5 days after the end of rental period. Additional delay in return costs 5 € per day.

Website
http://www.droam.nl/en/

ComfortWay
Instead of renting a MiFi router (see Droam), you can think of buying a device. ComfortWay is an international start-up which sells Mifi-routers linked to a low data roaming tariff. In 2014 they signed an agreement with Czech T-Mobile to use their platform. SIM card and tariff are only available in combination with the router.

MiFi
They sell two MiFis as a choice: Their routers are available online to be delivered in 3-15 days within the EU for free or plus 37 € by DHL Express paid by credit card, PayPal or bank transfer. Or in their outlets at some European airports. Top-ups can be made online by Mastercard, Visa or PayPal.
 * ComfortWay Lite looks like a rebranded Huawei E585: 2G, 3G, max. download 7 Mbps, max. upload 5.76 Mbps, connects up to 5 devices for 39 EUR including 5 € credit.
 * ComfortWay Pro looks like a rebranded ZTE MF60: 2G, 3G, max download 21 Mbps, max. upload 5.76 Mbps, connects up to 8 devices for 59 EUR including 10 € credit.

Rates
They offer two rates for EU and EEA data: Other countries (20+) like Canada, USA, China or Russia are only available for 0.29 €/ MB.
 * Business: 150 MB of EU roaming data for a daily flat fee of 6 €.
 * Standard: flat rate of 0.05 € per MB across the EU

As part of the deal, the SIM card is locked to the device and not available seperately. With their offer they mainly address business travellers. With a default data rate of 0.05 €/MB, they currently beat all "international" prepaid SIM cards in the EU.

Website
http://www.eng.comfway.com/