Do you want to control your project with an SMS or connect it to the Internet via GPRS if you do not have access to Wifi? Adafruit's awesome cellular breakout board, "Fona Mini GSM Breakout" is the best way to do what you want. With this little guy you can send SMS, data and voice. That's right. This thing will effectively convert your project into a phone.

This breakout board is just 1.75"x1.25" in dimensions and uses a tiny GSM cellular module SIM800 at it's core. It has a uFL connector for the antenna. With this module:

• Send and Receive SMS
• Make or Receive Voice Calls(Using headset or external speaker and mic)
• Send and receive data through GPRS
• Tune in to FM radio
• PWM/Buzzer vibrational motor control
• Charge a LiPoly Battery

On its own, this module can't do anything. It requires a microcontroller to drive it! We suggest and use an Arduino or any other UART microcontrollers.

Need a one which has a built in GPS? Check out Adafruit Fona Mini Cellular GSM + GPS Breakout Board

Also check the official adafruit's page for this product. They have tons of more info and tutorials.