Reinventing The (Training) Wheel

Gyrowheel essentially has a gyroscope inside. Gyroscopes are spinning wheels that exhibit a special property called precession. When a force is put at the top of a spinning wheel (such as a rider falling on a bicycle), rather than falling, the gyroscope simply turns, or precesses, in the direction of the fall. This occurs on normal bike wheels when the bike is traveling at higher speeds. Hence, it is easier to ride a bicycle once you "get going." Gyrowheel takes advantage of this property even when the bike is moving slowly. The disk inside Gyrowheel spins independently of the bike wheel. Thus, even when a rider is moving very slowly on the bicycle, the precession of Gyrowheel is still felt. If the rider begins to fall, Gyrowheel precesses under the rider's weight, restabilizing the bike.

Thanks To Keith at BagOfNothing