Actually, a bit of a gruesome idea I had was to look at NHTSA crash records and calculate the average probability of death at various speeds in my vehicle (Nissan Xterra). As you speed up and break the speed limit, a little % icon on the dashboard rises to indicate how likely you are to die if something goes wrong. I think the emotional impact of staring your fatality chances in the face as they steadily rise might encourage safer behavior for our monkey brains.