Little comfort if the vehicle behind is a fully loaded HGV that can't stop. I've seen what happens when a 38-tonner hits a stationary car and it's not pleasant.
Similarly it will be your fault if the car in front of you suddenly does a full on emergency stop for no apparent reason. Few people leave enough gap to stop in these circumstances.
Beeps and flashing lights are OK but having the car automatically apply the brakes for no reason is really scary stuff. Nothing worse than technolgy that doesn't work properly.
