I’ve looked at this stuff, because of its utility as an emergency communication system.
I’m not sure if any of the open standards are there yet, but that may just be, because there isn’t money to be made, so no commercial entity has approached it (like GoTenna, which appears to be the only successful one, but uses a proprietary protocol).
For emergency comms(remember, emergency services provided by the state don't monitor the ham bands, so can't call them), a $20 ham radio would work or just carry FRS radios.
FCC does allow use of a ham radio in a real emergency without a license.
> They would probably need some robust, non-problematic kit that could work in any environment.
Nothing is more robust than ham radio at 144/420 MHz. Even first responders use frequencies adjacent to this and has the same RF propagation characteristics.
For S&R teams, you could apply for LMR license. It is valid for 10 years.
I’m not sure if any of the open standards are there yet, but that may just be, because there isn’t money to be made, so no commercial entity has approached it (like GoTenna, which appears to be the only successful one, but uses a proprietary protocol).