GSM Playground description:
GSM Playground is a GSM Shield designed for Arduino based boards (Arduino Duemilanove, Arduino MEGA, Seeeduino Mega…). It is built on a well known and reliable GSM/GPRS Module GE-863 QUAD from Telit. This module is pretty small so it is placed directly on the shield PCB. The GSM Playground offers GSM capabilities plus other features like recognizing DTMF tones, measuring ambient temperature, and others.
GSM Playground specification:
GSM Playground accepts prototype shields or other boards with Arduino compatible interface. The GSM Shield uses digital pins 0 to 9 but the pins 6,7,8 and 9 can be also used for other purpose (they can be switched to high impedance). The GSM Playground is compatible with Arduino Ethernet Shield.
GSM Playground pinout:
For more detail: GSM Playground