The Project Lifesaver bracelet operates on radio telemetry rather than GPS. According to this item, some 805 public service agencies in 45 states are tracking missing people with the equipment from Project Lifesaver, a nonprofit headquartered in Chesapeake, Va. and it’s been 100 percent effective helping to locate 1,790 people since 1999.
It took me rather by surprise to see that equipment for Project Lifesaver costs about $8,000, and another $300 a year for battery and band replacements for the bracelets. Not per person, surely? Article on ScrippsNews.