We've known about Dean Kamen's work on the Stirling engine for hybrid vehicle use since the inventor introduced the DEKA Revolt late last year. According to some recently-filed patent applications, though, it would seem that Kamen has lots more up his sleeve for the good 'ol Stirling engine, including a possible hybrid scooter.
According to Gizmag, Kamen is thought to be using a prototype scooter featuring the Stirling hybrid powertrain at his personal residence on an island a mile off the coast of Connecticut. From the patent drawings, we can see a that the Stirling engine is mounted at the rear of the bike while a rechargeable battery pack for the electric motor sits under the scooter's floor.
According to the report, Kamen has invested some $50 million into the development of the Stirling engine, though it's unclear whether there are any possible production plans for this particular hybrid scooter.