Mandate that all firearms are outfitted with a GPS Safety Lock that prevents weapons from being used in public areas

1.) Every new gun (by say 2020) would be outfitted with a piece of hardware that would detect the physical global position of the gun.
2.) The government (or maybe even individuals) would designate "gun free zones" based on GPS coordinates
3.) When the gun is in a location of a "gun free zone" (whether it be a school, hospital, or even city) the safety is engaged rendering the gun unusable. When the gun owner leaves the zone, the safety again is disabled and the gun becomes usable.
4.) Green zones could also be designated such as the gun-owner's home where the safety can be off so that the gun could be used in self-defense