Going Electric
 

Ok so here's the deal... I'm trying to come up with a business plan for a class for a company that would be able to increase MPG in existing, used, on the road, cars...
My first idea is to try and find a method of converting a gasoline powered car to a hybrid electric/gasoline... Would it be any where near cost effective? How long before we'd have the technology to do so?
How about ways of converting cars to run on electric power or interchangeable battery packs or things like that? I know its possible, but would any normal not-environmentally concerned person ever do it?