Electric-powered wheels

So I was thinking (again on the drive to work) that it would be nice to have a car who's wheels were powered by electric motors. Then these motors could still be powered by a standard gasoline engine, but you would have greater control over things such as traction and fuel economy. Say for instance you wanted to save gas on your drive; you simply switch off all but one wheel and that is used to move your car forward... if the road becomes slippery or icy you could "turn on" the other wheels to add traction while reducing fuel economy. Seems like a good idea to me, especially with gas prices as high as they are. It would be really usefull on my Wrangler; saving me lots of gas on the drive to work and back.