The problem with all these alternative energy cars you hear reported is that they are so frequently "vaporware" so to speak. They get reported on while they are still some inventor's brainchild. And, while the technology may exist, there is a HUGE gap between a viable theoretical design and a viable business model. I think a lot of people are getting jaded after constantly being bombarded with these types of concepts and never seeing anything similar make it onto the market.
Bottom line, there is no significant technological hurdle between us and vehicles with this kind of capability... it's mostly logistical, political, marketing hurdles.