BBot 2.0 is a custom-built self balancing robot that features an integrated motor driver / controller, onboard micros that measure inertial sensors (calculate tilt), and external port connectors as well as an I2C bus header in case a larger motor driver is needed. More information here. Video demonstration after the jump.
Self balancing robots have become very popular in recent years. BBot will be at the top of the heap soon since it is soon to have Bluetooth capability and be able to balance on a ball