I like the seatless-unicycle. When I was a kid, I got a tricycle wheel with pedals attached and tried to learn to ride it like a unicycle. Only succeeded in going 2-3 pedal revolutions. (Well, I never learned to ride a unicycle either...) The ones in the video had taurus-shaped hubs with pedals attached on straight shafts, rather than central hubs with bent pedal shafts.