One of California's largest firearm stores recently added a peculiar new gun to its shelves. It requires an accessory: a black waterproof watch. The watch's primary purpose is not to provide accurate time, though it does. The watch makes the gun think. Electronic chips inside the gun and watch communicate with each other. If the watch is within close reach of the gun, a light on the grip turns green. Fire away. No watch means no green light. The gun becomes a paperweight.