There are many companies getting ready to produce such a machine. Typically, they're called "carvers". Even Harley has one in the works.
More articles here- http://www.gizmag.com/motorcycles/
(you'll have to rummage around for them)

As a long-time odd-ball vehicle fan and sidecar pilot I have to admit an interest in these. The sour note is the high cost- well beyond that of a really good motorcycle.