Not my area of experience, but couldn't you each carry a Garmin "Chirp" programmed to each others GPS unit? only $23.00.
https://buy.garmin.com/shop/shop.do?pID=74811&ra=trueThis would give you the advantage of having a GPS unit plus a way to locate someone who is nearby but out of sight.
The reliable range of the Chirp is said to be '30-'40, the battery lasts a year, and I'm thinking it is about the same power as an av beacon.
No affiliation
Interesting! Never heard of it before.
Seems like it would be of limited utility. You've only got 10m range under ideal conditions. If conditions are ideal, you probably don't need a Chirp.
Range: up to 32 feet (10 meters)
Tips:
Do not mount the chirp inside a metal container.
Do not bury the chirp.
Do not put the chirp in water.
A compatible Garmin device should detect the chirp within 10 m. For maximum transmission range, allow the chirp to have an unobstructed view in all directions [emphasis added].
Still, this may be the shape of things to come. Perhaps units with more range will become available. Parents could slip one in a child's pocket. Now, that would be nice at the County Fair!
HJ