Self balancing robot based on Arduino UNO ATmega328 microcontroller 
http://arduino.cc/en/Main/ArduinoBoardUno/

Hardware list:
    arduino uno
    dual mc33926 motor carier
    lipo 11.1 v / 1300 mAh power cell
    MinIMU-9 Gyro
    2x Motors, 12V 1A (max 2A), 50:1 gear ratio, 6kg/cm peak force
    big weels
    jy-mcu v1.02 ( Bluetooth RF Transceiver )



Operation basics:

    Read raw gyro
    Read raw accelerometer 
    Calculate current angle
    Calculate engine torque with PID controller 
    Correct current position
    Do the same thing over and over again ( should be around 100 Hz )

Notes:
I decided against Kalman filter in favor of Complementary Filter 
as its has almost same performance but without the complexity of Kalman filter.


video:
http://www.youtube.com/watch?v=coYkNLxFi1g