The Segway Centaur is the newer, younger brother of the Segway that just about nobody—unless you're Steve Wozniak or a Chicago beat cop—is riding. This four-wheeled Segway looks more stable than the previous one, even when it's up on its hind wheels. The Centaur features a seat, handlebars, and the same type of engineering that went into the commercially unpopular Segway.
We have to say, it looks like it goes pretty fast and could be fun to ride. No chance at all seeing this on city sidewalks (maybe bike lanes?) though. Just a concept for now, so we probably won't be seeing this for a few years at least.
Segway Centaur [TechEBlog]