Child Locator Device/GPS

I am looking for a product that a child can wear that will alert the parent that the child has moved away from their location. It will give a beep or chirp and the light may flash. The parent should be able to program the distance that the child's tag can be apart from before it starts beeping. Also, if I can find a product that can be tracked through GPS technology for older children who may be playing around the home or in the neighborhood and teh parent needs to track their whereabouts.