the "Black Box" is the air bag SDM (sensing diagnostic module) it records all that stuff. throttle, brake, speed, seat belts, steering wheel position if a sensor is there. we have insurance adjusters come out from time to time with there lap top and down load them.
this is why you need to replace the SDM if your air bags go off. it locks all that data in a read only memory just for this use.
OnStar can't record all that stuff because it happens so fast.