4th Amendment & GPS Are we secure in our travels?

IF the Govt required that all cars have a GPS(and how many want OnStar and such that do just this?) then this issue would come up again. The problem is that so many fools would go along with it. Soon we would have no privacy, as we are already going to. The idea though is the police could sit around and follow your car, so ONE car isn't as big of an issue as if it came to EVERY car.