Garage builders are a fascinating group, especially when they have time on their hands and a pile of parts or a wild idea about the next big thing. I followed a link a little while ago and found myself looking at all of these kinda crazy but very cool monowheels and dicycles. It makes you want to dig a little deeper into the junk pile and see what you have handy. You might be able to build one of these yourself.
Kerry McLean recently built a 225 horsepower V8 monowheel that received a bit of publicity and he even sells various versions of his creations but they are only the most recent examples of an idea that has been floating around for a very long time. Some earlier wheels are even better because of the far more limited workshops where they were built and some look like they never would have worked at all but all of them are interesting.
Dicycles are even more uncommon than monowheels. These have two wheels in parallel with some sort of seat suspended in between, kind of a Segway on steroids idea except no fancy gyro stabilizer is necessary since gravity should keep everything properly oriented. Steering would be some form of differential power or braking.
I can only imagine what some of the custom builders could do with these ideas if they took a little time to play with them, especially the dicycles.
Both monowheels and dicycles are an interesting bit of motoring history and if you have not looked at them before, the two links below have many examples from over the years, they are definitely worth a bit of your time.