Features:-

+ Chip: SIM800L
+ Voltage: 3.7-4.2V
+ Support networks: China Mobile, China Unicom and global quad-band network
+ Module size: 2.5cmx2.3cm
+ TTL serial port for serial port, you can link directly to the microcontroller. No need MAX232
+ Power module automatically boot, homing network
+ Onboard signal lights all the way . It flashes slowly when there is a signal, it flashes quickly when there is  no signal


Useful Documents:-

+ Datasheet: http://www.adafruit.com/datasheets/sim800h_hardwar...
+ AT Command Manual: https://www.adafruit.com/datasheets/sim800_series_...
+ TCP-IP Application Note: http://www.adafruit.com/datasheets/sim800_series_t...
+ IP Application Note: http://www.adafruit.com/datasheets/sim800_series_i...
+ SSL Application Note: http://www.adafruit.com/datasheets/SIM800%20Series...
+ Email Application Note: http://www.adafruit.com/datasheets/sim800_series_e...
+ They have also created an easy to use library: https://github.com/adafruit/Adafruit_FONA_Library


Tutorials:-

+ http://www.ayomaonline.com/programming/quickstart-sim800-sim800l-with-arduino/
+ http://www.seeedstudio.com/recipe/358-the-ultimate-child-tracker.html