[scolton] made a nice self-balaced vehicle based on two DeWalt cordless drills and an Arduino Nano:

Segstick is a self-balancing…well, literally some kind of broomstick I found in the MITERS workshop. It is powered direct by two DeWalt cordless drills chucked to two 6″ wheels. The controller is an Arduino. Additional supporting devices include an Inertial Measurement Unit (IMU) from Sparkfun and two motor drivers from Pololu .

see the compete how-to on [Instructables]