Is this what you're talking about
After a google search it seems that the technology is quite mature, but it all seems to be focused on heavier trucks and comercial markets at this time. It also seems that full hydraulic hybrids could be on the way farther down the road. Thinking long term the hydraulic route as a whole seems to have more potential to actualy work without significant disadvantages than the electric hybrids do, but I guess only time will tell.