In all honesty I see this causing more accidents than it could prevent.
Let me elaborate. Whenever you get scared, you have a tendency to over physically overreact. An example would be slamming down on the gas when you think you're about to hit someone, or jerking the wheel when you're about to hit something. Many times the way you over react causes more damage than you probably prevented.
This system could possibly frighten people in in a similar manor. One example would be a person leaning over and not realizing they were swerving and hearingthe nice little BEEP BEEP noise. The noise then causes them to jerk their steering wheel in the opposite direction of the way they were swirving - in turn losing control of their vehicle at high speeds.
Just something to think about..