In the video, Sphero commands the toy car where to drive. It does this through a trackball similar to the one used in a computer mouse or in the arcade game of golf. Sphero sits on the trackball’s wheels and his weight and momentum cause them to move. The wheels have encoders that then tell the car what direction Sphero is moving by sending out x and y coordinates of the movement to the motors. Roll Sphero forward and the car drives forward. Roll Sphero to the right and the car turns to the right.
Skylar’s Sphero car intractable shows you how to make your own.