Minibike

The optimum solution to a human-powered mobility solution that is faster than walking but takes up less space than a folding bike has not yet been solved to my satisfaction (no doubt skaters and bladers would disagree), so here's my ten cents worth.

The key is to harness a natural walking gait in a similar fashion to a cross-trainer and translate this power to wheelled motion. Two inline wheels (like a bicycle on a smaller scale) sit at the bottom of a stem that goes between the legs. The wheels are powered by forwards and backwards foot/leg motion on moving arms, which is translated to rotary motion in the wheels via a gear and chain mechanism that is hidden within the stem of the device. The body of the device also acts as a steering column, allowing a pair of handle bars to control direction.