[Lx]

Imagine a tricycle in reverse, where the big wheels are at the back and the small wheel is in the front. If you rotated one of the big wheels in a clockwise direction and the other in a counter clockwise direction, voila, you have a device that can turn completely around with a zero turning radius. Just don't put the small balance wheel ten feet out or you'd need that much room to rotate even though you have a zero turning radius. In other words, not exactly a breakthrough.

[spycatcher]

You just described this with an extra appendage that stick out and spins around hitting whatever is in it's path. This is much more efficient and can only be improved in this sense with a perfectly efficient self-balancing unicycle design.

[Don Joe]

"Imagine a tricycle in reverse, where the big wheels are at the back and the small wheel is in the front."

Now imagine stopping on a dime with that vehicle -- without getting skidmarks on your nose.

A three-point device is very stable -- when stationary. Abrupt starts or stops will get ya. Inertia and momentum are your enemy.

This vehicle uses those forces, rather than having to work around them.