The inexpensive SPOT Satellite communicator uses the same satellites used for sat-phones to send a Globalstar Simplex data (uplink only) SMS like signal to a terestrial phone or email address. It is useful when out in areas that there is no mobile service. For $100/year you can either send GPS tracking info, a distress signal with location, or with bluetooth pairing to a phone send short messages.

There is a N9 app linked below already developed for this but a N900 hack would be great for the rest of us. There is also info on how to bypass the internal GPS messaging system to directly access the communications module to allow all kinds of communications hacks beyond just location. This communication is over serial protocol using either a cable, a bluetooth to serial adapter, or by connecting your own processor.

https://github.com/travisgoodspeed/goodspot
http://hackaday.com/2011/10/01/hacki...e-information/
http://hackaday.com/2011/12/05/rever...as-an-example/
http://travisgoodspeed.blogspot.co.i...th-rfcomm.html
http://natrium42.com/projects/spot/

Nobody interested in cheap satcom for the N900?