I have several PIC projects that sends AT (ETSI) commands to GSM modems to send, receive and process SMS for remote monitoring and controls. My favorite uC is the PIC12F675 8-pin microcontroller with ADC and have internal oscillator that keeps parts count low and hardware simple. One application I am using now is to monitor the wind velocity and direction, and solar radiation at home. The Nokia 6210 phone with GSM modem at home reads and interprets my incoming SMS messages, checks the weather data and sends it back via SMS to my mobile phone wherever I am. This gives me a more accurate weather update than the weather news. It also records the wind velocity distribution and direction using the internal eeprom that can also be sent via SMS using a data-dump SMS command. I hope this is of interest to you.