Can car seats be any safer?

I posted the following to the Car Seat Questions board on Babycenter, and am interested to know what you think:
On a recent Babycenter thread, I cheekily suggested a seat that fills with foam upon impact (which might not be all that safe, I know), but what else could there be?

With higher rf weight limits, higher weight FF seats, and SIP becoming the standard for new car seat models, what other safety features could manufacturers consider adding to car seats?

One thing that I could see is emergency locking retractor belts in car seats -- the kind that are sensitive to rapid deceleration, and have an inertial mechanism device that pulls the seat belt taut upon impact? I think the Safeguard seats had them (correct me if I'm wrong), but that seat was so expensive, and I believe Safeguard is no longer making that model.
Other ideas?