Sony filed a patent for a motorized skateboard that riders steer by shifting their weight.

The filing, published in November, 2006 describes "a vehicle which can travel in the front and back direction and which can turn by right and left wheels rotated when a rider riding on a step-board moves the position of rider's balance from the center of a vehicle base."

In other words, Sony envisions a device similar to a Carrom Balance Board — a board atop a cylinder that you try to balance on — except with two or more motorized wheels that you drive by shifting your weight.

The described device — a skating roller board — would power down when not bearing weight, a situation that might occur following a fall, for example.

In September, 2006, Segway, Inc. issued a voluntary recall of its two-wheeled electric scooters for potential malfunction that "can unexpectedly apply reverse torque to the wheels, which can cause a rider to fall." The company said it had received six incident reports possibly attributable to this issue.

President Bush famously fell from a Segway scooter in June, 2003, though the machine's maker blames that tumble on operator error.

Sony appears to have considered such incidents because it also envisions three- and four-wheel versions "to improve stability of the vehicle."