I think it might be time to create a general-purpose communicator. A as-simple-as-possible device capable of communicating as reliably as possible with other devices like itself as well as ideally other types of communications devices.
There's many things like this, but in my opinion they have unacceptable limitations.
I'm thinking something based around a software-defined radio (SDR) so that it can adapt to communicate with most any sort of wireless system. In the most extreme scenarios I think that good-old-fashioned analog voice communications (CB/ham radio, etc.) are always going to hold the line so whatever this is and whatever sort of "digital" capabilities it might provide should be supplemented with the ability to fall-back to these methods of communication.
I don't know much about SDR, so I don't know how reasonable it is to have a device that can reconfigure itself like this without the need for a full-blown general-purpose computer and the associated software, etc. If possible the ideal would be to make all that's necessary self-contained within the device, but if that means cramming a whole computer with associated screen/keyboard/etc. and the power demands all that places on such a system then I'm not sure that's the way to go. Alternatively if it's possible to store several configurations that have been built in advance that allow the device to reconfigure itself in a self-contained way, that might be good enough.
On top of the SDR and basic analog voice radio capabilities I'd put some level of digital communication facility as well. If possible this would re-use the SDR hardware for other types of wireless communication (WiFi, etc.) but again I don't know the practical limits of this technology. Digital modes open up the possibility for store-and-forward based networks which have advantages over the "realtime" nature of analog voice comms, and of course there's options for keeping messages more private as well (although I wouldn't recommend relying on this, nothing beats a one-time-pad). Something along the lines of a microcontroller running Micropython should be more than enough for this task and easily fit within any imaginable power budget.
Something that might be helpful is a way to share location information among devices. I'm not sure if this means including a GPS receiver (maybe another thing that the SDR could do?). There's lots of imaginable applications for this but if it adds too much complexity it's not a requirement.
Other nice-to-haves would be a case big enough to house a solar panel capable of topping-up the battery and sturdy enough for field use. Something as large as an old-fashioned Walkie-Talkie handset would be fine for this and provide plenty of room for batteries and excess case material.
Jason J. Gullickson, 2026