Cheap satellite phone service. $50/month for 120 minutes of satellite phone time throughout North and South America, Europe, Asia. It’s a normal cell phone too, so you don’t have to use your satellite minutes when you’re in a city or near a cell tower. Oh, and it’s also a 9.6kbit/sec modem, even in satellite mode.
The phone, a Qualcomm GSP-1600, lists at $650 new, but you can find them used for as little as $450. They are a favorite with back-country hikers.
[This model is rather dated. If you are using a new sat phone, whether a Globalstar or otherwise, please let us know in the comments. -- SL]