Raspberry PI GSM Add-on V2.0 is customized for Raspberry Pi interface based on SIM800 quad-band GSM/GPRS/BT module. AT commands can be sent via the serial port on Raspberry Pi, thus functions such as dialing and answering calls, sending and receiving messages and surfing on line can be realized. Moreover, the module supports powering-on and resetting via software.
Documentation please see on this page.