Wavecom makes a GSM modem that can be used for this purpose. It takes a SIM card and has a serial port to connect to a PC or server. You can communicate with it using standard modem AT commands.
...

I am connecting to a servlet in a seperate thread. The connection goes fine, and I get in data back. But when I try to update the screen by calling amethod in the System thread from the connection...

It should be between 0-11. Sun's Calendar class has always used 0 indexed months. My guess is that someone did a poor job of emulation on the 7210.

-David