Some time ago, I read about a new design for an integrated starter/alternator which was so powerful that it could start the car intantaneously, such that the car could turn itself off automatically, and restart upon stepping on the accelerator. This design was not for a hybrid, but for a standard gasoline engine.
Link
I guess what's holding this back is the need for a higher voltage electrical system. The Japanese will probably be first to introduce such a system, since Detroit has waffled on this idea.