I am using cellular phone in my remote control and alarm application (www.geocities.com/dlapuh - sorry, it's only in slovene language). I control the phone by AT commands. For unsupported AT commands (like sending SMS) I use AT+CKPD and emulate pressing on keypad (I emulate ericsson chatboard). I can make or take call, send DTMF and send SMS (this takes some time) without any physical press on keypad.

regards, Damjan