Something like that exists with the RECCO system. https://en.wikipedia.org/wiki/RECCO https://en.wikipedia.org/wiki/RECCO Not quite an arbitrary Personal Loca

Something like that exists with the RECCO system. https://en.wikipedia.org/wiki/RECCO https://en.wikipedia.org/wiki/RECCO Not quite an arbitrary Personal Locator Beacon, but it can help rescuers home in from a distance. It's cheap because the tag is just an antenna and a diode.