...A generator-equipped hybrid? Rig something up to have a conductor move through a magnetic field as the wheels turn, therefore in theory charging the electric motor? Other than that it would be a standard hybrid, electric motor running to 40mph or so, and in theory having infinite power as it ran?
your idea will result in much less than 100% efficiency, ie: wont work. the generator will make the motor work harder which will require more energy to move the car along, eating up energy faster. You can generate a low amount of power without straining the system, but the power needed to run the electric motor will put a large strain on the motor....
I believe some hybirds have 'regeneration brakes' that recaptures energy spent to propel the car by generating energy by slowing it down.
Also, all cars have generators, or 'alternators' that provide electric for ignition, radio, and other onboard electric accessories. As far as I know, they're all run off the engine. The further you get from the engine, the more power is lost to friction (transmission, differential, u-joints, tires)