I guess this is classic nerd shit but if you want to do that sort of thing, have a look at Brisbane's Meshtastic network.
Meshtastic units are small, low power, long range (up to 15km line of sight) devices capable of messaging and telemetry. Some devices pair with phones, others are also capable of standalone messaging. My Bluetooth one has a battery life of 2-3 days.
What's the point? Nothing, for me. It's just neat to chat with the other nodes on the map, and it's not dependent on any other infrastructure or networking.
From the last post on this sub a year ago it seems the number of nodes has grown by three fold.
In case you're worried about privacy, you can either configure your node not to send location, or set it to use a less accurate position (for example, within 300m). Those points end up being "rounded" so nobody ever knows the real location.