Segway is now obsolete, the Honda U3-X

The U3X is an electronic unicycle manufactured and distributed by Honda. Currently only available in Asia, the U3X would retail in North America at about $660. The U3X is said to be a technology breakthrough and the world's first driving system capable of 360 degree movement.
a compact experimental device to provide free movement in all directions just like human walking - forward, backward, side-to-side, and diagonally. Honda will continue research and development of the device including experiments in the real-world environment to verify the practicality of the device.

This new personal mobility device makes it possible to adjust speed, move, turn and stop in all directions when the rider leans their upper body to shift their body weight. This was achieved through application of advanced balance control technology, robotics research, and the world's first* omni-directional driving wheel system (Honda Omni Traction Drive System), which enables movement in all directions, not only forward and backward, but also directly to the right and left and diagonally. (think of the wheels on the "I Robot" vehicles)

In addition, the compact, one-wheel-drive personal mobility device was designed to be user friendly and unimposing to people around it. This is achieved by making it easy for the rider to reach the ground from the footrest and by seating the rider at roughly the same eye level as a person standing.



Tere posted a bit more about it, with images that make it easy to understand the multi-wheel that this rides on, it can go forward/backward or side/side: http://justacargal-s.blogspot.com/2011/02/honda-omni-personal-mobility.html

There is a similar wheeled thing http://www.youtube.com/watch?v=WOOoFEKiK8A that doesn't have a seat, or a chance at succeeding when the Honda has a seat, the Segway has a hand hold, and this has a reliance on the balance of the operator. Never going to make it.