The GPRS/GSM Shield provides you a way to use the GSM cell phone network to receive data from a remote location. The shield allows you to achieve this via any of the three methods:
Short Message Service
The GPRS Shield is compatible with all boards which have the same form factor (and pinout) as a standard Arduino Board. The GPRS Shield is configured and controlled via its UART using simple AT commands. Based on the SIM900 module from SIMCOM, the GPRS Shield is like a cell phone. Besides the communications features, the GPRS Shield has 12 GPIOs, 2 PWMs and an ADC.
Because SIM900 peak current more than 2A. This shield must work with a external DC9V power supply.
If you are using MEGA2560. Just need to connect the middle pins of RX and TX jumpers to RX1 TX1 on Arduino Mega 2560. And change the code setting.
Based on SIMCom's SIM900 Module
Quad-Band 850 / 900/ 1800 / 1900 MHz - would work on GSM networks in all countries across the world.
Control via AT commands - Standard Commands: GSM 07.07 & 07.05 | Enhanced Commands: SIMCOM AT Commands.
Short Message Service - so that you can send small amounts of data over the network (ASCII or raw hexadecimal).
Embedded TCP/UDP stack - allows you to upload data to a web server.
Speaker and Headphone jacks - so that you can send DTMF signals or play recording like an answering machine.
SIM Card holder and GSM Antenna - present onboard.
12 GPIOs, 2 PWMs and an ADC (all 2.8 volt logic) - to augment your Arduino.
Low power consumption - 1.5mA(sleep mode)
Industrial Temperature Range - -40°C to +85 °C