There are already gps bracelets and watches etc specifically designed as a tracking safety device where parents can know instantly on their cell phones where their child is. It even alerts them if the device is removed. Do a google search to find out more.
On the main issue of safe stores or homes, it would work amazingly if they all had cctv cameras that were either networked or internet linked. Then the issue of can we trust this guy to run a safe place is sorted because they cant hide the fact that a particular person or child entered the store. And faces can be picked out by computer in seconds. In the UK, police cameras pick out faces of known trouble makers in seconds amongst crowds of 85,000 at soccer matches.