Waze is a smartphone navigation app that uses crowd sourced data to provide route and traffic information to users.
It has turn-by-turn navigation, audible alerts, real time traffic and road speed, and the ability to plan the best departure based on arrival times, but the most important feature is police tracking.
Users can report police that they encounter along their routes in one of three categories: visible, hidden, and other side.
Drivers are then alerted to police that are ahead on their route with both an icon and a “Police Ahead” announcement, and it is even noted on the route choice screen.
The tradeoff is that you must allow the Waze app to report your location and speed to them, but that is a price I am willing to pay.