GyroBike a spin-out of Dartmouth College with a gyroscope device that helps kids learn to ride a bicycle without training wheels.

The Gyrobike employs spinning flywheel inside the front wheel that uses gyroscopic precession to provide a bike moving at 2.5 mph with the natural stability of a bike moving at 10 mph.
This natural stability has been demonstrated to enhance the process of learning to ride a bike.

Pretty cool idea. The fact that the Gyrobike is available as aftermarket product could give it huge sales potential.
The GyroBike product will sell for around $39 and be on the market later this year.
More details on CNET and on the GyroBike site.

Industrial Designers at Purdue University also came up with a bike design for kids learning to ride.