Dutch vehicle designer Allert Jacobs knew that his fuel-sipping, shell-encased motorcycle was street-legal. Unfortunately, the police didn’t, and impounded it after pulling him over during a test run.
It's not terribly practicle, but I'd buy one for tooling around town and driving to and from work. My Cocours averages around 50 mpg (depending upon who much speed-whoring I do), but this is far better. Several years ago, a guy in Switzerland modified a BMW motorcycle with something along these lines, but he had added stabilizers that would flip down at low speed so that you didn't have to worry about falling over. I saw that on either Discovery Channel or the Learning Channel (before they became enamoured with Kate and whatshisname who made 8) or maybe the Science Channel. I think the show was "Beyond Tomorrow". The hosts were Australians and they featured some really cool technology.
I think that if he puts spring/hinged flaps so that you can put your feet down in a "wide" stance, this shell of his has some great applications for motorcycling.