The only reasonable numbers are zero, one and infinity.
-- Bruce MacLennan, Principles of Programming Languages.
Some time ago I built a self-balancing two-wheeled scooter. Since then I realized that two wheels are redundant, and only a single wheel is needed to make a ridable vehicle. A vehicle with a single wheel is much smaller and lighter. It weighs under 30 lbs and is easily carried with one hand when going up stairs or on public transportation.
The Electric Unicycle's only control is the on-off switch. The rider controls everything else by shifting his weight. You lean forward to accelerate, lean backwards to brake, and gyrate your arms wildly to turn. With a little practice you can get more graceful and keep your arms mostly by your side.
