i hope it can help u !!!
u can lock in the phone by PIC with AT-command too
mean u write code in PIC with AT for read the SMS from phone
i think all out of ur mine!!! but it can help u ....
the mobile phones has a build-in modem this allow your microcontroller interface or connect then transmit or receive data/instruction depending on how you program/used the microcontroller. some mobile phones has AT command that is showed in the internet. the Nokia phone has AT command that is so easy to used. the problem is the schematic of the unit (depend on the unit of mobile phone) because it is confidential you may ask the schematic of the unit to the company! the schematic provide the information and configuration of pins you are using to command the phone to transmit/receive the sms/call.
the microcontroller uses the UART to interface to the modem of the mobile phone. also the uart has a driver, for example, i what to connect the microcontroller to my PC i used the RS232 to attached to my microcontroller then the UART is attached to its driver such as MAX232. this IC allow you to receive and transmit data over RS232. gets? hehehehe.