Over the years, many people have installed Whistler and other radar detectors in their vehicles.  Unfortunately, if you wind up being pulled over for speeding, having one of these devices on hand can cause a number of problems.  On the other hand, a car dvd navigation system that delivers speed warnings is a much safer option.  Among other things, it will simply alert you each time that your car goes over the speed limit.  This can be especially helpful if you are driving in a strange area, and do not know where the speed traps are.  Even thought these devices may be a bit more expensive than other models, you will appreciate saving money on car insurance and speeding tickets.