This Looks Like Tons of Fun!

Let me introduce you to the cool-looking Gaus Wheel from Hungary. I might be too old to be doing big Ollies on a skateboard, but I might be tempted to take one of these for a blast in a park or a parking lot. Check out the videos on their website, they're very cool.

The low center of gravity should make it a lot more stable than a unicycle, which would make it easier to ride for most of us. I'm not sure how you go about stopping it, but I'm sure you'd figure it out before you lost too much skin. Wasn't that half the fun of riding a bike as a kid, finding your limits? I don't know if anyone is importing these into the US yet, but I'm sure you could find a way to get one if you really want it.