Emergency Vehicle Alert

It would be helpful to we First Responders if every car were equipped with an audio / visual device that would alert inside the vehicle when an emergency vehicle was approaching. A sensor on the outside of the car could detect a siren and activate something like a small blinking red light on the dashboard. Almost on a daily basis I am forced to pass a vehicle while responding that generally has no clue I am behind them. Too many unecessary destractions in the cars today (ie. cell phones). Thanks ~ Battalion Chief Steve Nash