Wow, pretty interesting. The design is phenomenal and original, but I believe it only to be useful by people such as kids or anyone who does not want to go "fast". They only go about 17 mph, and don't hold very much gas.
But hey, if that's your thing, more power to you!
(that last comment was not directed at you, sk8freak8989, but people who might be interested and who might purchase one)
They never seem to catch on for some reason. They popped up in the late 1800's and seems like every 20 years theres a new design, but they don't stick around. I like the idea, though it seems like it could have some small issues. The main thing I don't like is the fact that the fuel travels to the engine through the hollow axle and through some type of banjo bolt. I think that the high wear on that location could cause it to leak fuel should the connection get worn. The engine doesn't idle when you come to a stop, kind of an interesting design. Its possible it was used to decrease emissions. The price does seem to be below other wheel motors such as the sachs saxonette.