Yes you can now buy a motorised monocycle (not sure of the correct term) if you're in Europe: 'Wheelsurf.nl' (http://www.wheelsurf.nl/). While these have been built by several different people in the past these guys seem serious enough to have built 50 already. 4500 Euros will get you one of these cool wheels.
If these become popular imagine the tricks which people will start doing in them...
The Wheelsurf site is advertising with Google. If you search on "monowheel" at Google you'll see their ad. If you search on "unicycle" you'll see their ad on the second page of the search results. The ad has probably popped up on the Google ads here (Unicyclist.com) too, but I haven't noticed.
