Hi Ed, I’ve looked at similar technologies which have popped up in the last two or three years. Mostly aimed at getting remote area emergency comms. There is one fundamental flaw in all of them. They rely on a significant “critical mass” of people carrying and using them at the same time, so relay is possible.
For emergency use I suggest a simple PLB on the Cospas-Sarsat satellite system.
For two way comms it’s hard to beat a InReach device, now owned by Garmin, which uses the Iridium satellite network (currently being refreshed - https://en.wikipedia.org/wiki/Iridium_satellite_constellation#Next-generation_constellation). You can Spot yourself using this, anywhere on the surface of the globe with a moderately decent view of the sky.
I have personal experience of both of these systems.
Edit: just spotted Andy’s reply… his was similar to mine, if a bit more direct