I’m surprised that the Orbitwheel hasn’t been mentioned on WheeledThing before. It’s been advertised in the Skymall catalog for a while, with photos showing a cheerful Asian woman posing in a pair of Orbitwheels. We know she is only posing because she doesn’t have any broken bones.
Videos exist of people using these, on flat surfaces, at low speeds.
On the plus side, they sell for only about $100 a pair.
More details on their website, http://inventist.com/index.php?option=com_content&view=category&id=10&Itemid=118