The Noah is a motorized unicycle designed to use the human driver as the control device, using how you lean forward, back or side to side to determine acceleration, braking and turning, without the need for pedals or buttons." Click here for first picture in gallery.
The two tires act as stabilizers through turns as they can shift up and down against one another and give you more control. If they spun independently, you could even twirl in place.[via Dvice]