Dog and cats collars who have already built in GPS trackers. Every collar comes with their code, then you enter the code in a APP and it activates, then you can start tracking your animal. The collars should be like silicone, so you could put the GPS in them( like in the picture, but they need to be thicker, so you can put the GPS and so the animal cant break them easily).
Also there would be at least 10 colors, most likely pastel. And you could custom the collar- adding a phone number, animals name on the collar.