Try the Popular Science or Popular Mechanics web sites. Periodcally, readers post such info, and there have been articles in the past about this type of technology. It does exist, as GM. Retro fit for any GM vehicle is about $250k, so take it from there.
As long as you don't care about any sort of warranty that may still be on your vehicle, it might be neat to try. However, what is the ROI? How long before your fuel savings pay for your investment?
What happens when the price of oil drops? At what price point does your investment become a non-recoverable expense?