All countries2

There are international SIM cards together with so-called mobile Hotspots (also called MiFi) on the market offering "worldwide" data roaming or at least in major regions. Their offers are collected here in this "all countries" section. Their data rates are often more expensive than on the national level. So always compare with local SIM cards and roaming offers in your country. Although you won't save much using these cards, they may be a good option for frequent travelers and people travelling through multiple countries. For Europe alone, check the European Union section too.

''For a better readability this article is split into two separate parts now. This first part below is dedicated to international (data) SIM card offers. In a first article stand-alone data SIM cards are featured.''

PART 2: Worldwide Data SIM Cards with Wi-Fi hotspots
The combo approach of a mobile hotspot together with a data SIM has the main advantage, that it offers a complete solution. You don't need to care about frequencies, compartibility, and how to connect your device. You simply link all your devices by Wi-Fi with your hotspot. This is much easier if you travel in a group, stay together and want to have a common solution. There are offers for purchase as well as rental. If you decide to buy or rent your Mifi, you will cetrainly have higher start-up costs, but maximum compartibility and service.

GlocalMe
to be added soon

skyroam
to be added soon

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 (Mobile Hotspot)
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 mostly. Top-ups can be made online by Mastercard, Visa or PayPal.
 * ComfortWay Mini 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 € per 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/

Goodspeed
Goodspeed is a brand created by the Finnish Uros Ltd. They follow a different approach in renting or selling WiFi routers for roaming data. They teamed up with Chinese manufacturer ZTE to develop the MF900.

MiFi
Their new WiFi hotspot is called MF900 and has been released in summer 2015. It can take up to 10 SIM cards and gives up to 14 WiFi or USB connections simultaneously. It covers all 2G, 3G and most 4G/LTE frequencies used worldwide and battery lasts for 12 hours. It's sold or rented exclusively through Goodspeed online and its sales channels:
 * for purchase: € 239
 * for rent: € 19.90 per month in a 24-months rental contract

Data rates
Data is given out on day passes for each respective country seperately. Three tariff lines are offered: On the device, you can use your own SIM card(s) too. This is limited to one home SIM on the Lite line and unlimited on Pro and Business lines.
 * Lite: no base rate, € 16.50 per day gives 1 GB in most EU countries and 500 MB in other countries
 * Pro: € 9.90 per month base rate plus € 5.90 or € 9.90 per day for 500 MB or 1 GB depending on country
 * Business: € 14.95 per month base rate for larger quantities from 5 devices, rates the same as Pro.

In summer 2015 around 77 countries around the world are supported or at least announced to be covered soon. But you still need to have (or buy) a seperate SIM card (or day pass) for every country.

Website
http://goodspeed.io

Cellhire
to be added soon.