I've noticed a number of times, mostly on motorways that people braking sharply ahead will sometimes use their hazard lights to warn drivers behind them. So, my though was in regards to brake lights and that when a certain amount of pressure is applied to the brake or based on the speed in which the brake is applied, the brake lights should flash, or an additional brake light should flash to warn drivers behind that you are braking suddenly.
Of course we should all be keeping a safe distance anyway but this obviously doesn't happen always.