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=true

This 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