One option I've been looking at is the LoRa transceivers that have come out. A couple have bluetooth 5.0 baked in so you could realistically make a really low part count bridge for your phone to let you send encrypted mesh networked texts to other people running similar hardware. There's at least one person working on this I know of but they're not super forthcoming about source.
As for wifi, it's worth noting that while you can get a ton of gain, you do so by making the signal directional so long story short you always cover very roughly the same volume, be it a long super skinny wedge, medium donut or a small sphere.
Huh. Anything with GPS freaks me out. Even WiFi, now that Google etc have mapped so many damn APs. Or cellular, of course.
But then, here I am on a wired uplink. I guess it's just that I trust my understanding of nested VPN chains in Linux. And that I trust the hardware and software enough.
Android and iOS, though, I don't understand or trust.
You make a good point about WiFi. Not going transcontinental with that. Except adjacent continents, maybe.
If you don't like using your phone, theoretically anything with bluetooth would work with the bridge, or you could just add a microcontroller and a little keyboard and display to have something self contained. Something like the toy messenger everyone is hacking to open garage doors.
As for wifi, it's worth noting that while you can get a ton of gain, you do so by making the signal directional so long story short you always cover very roughly the same volume, be it a long super skinny wedge, medium donut or a small sphere.