Imagine if the radios we all carry with us everywhere could be programmed to communicate with each other.

(I'm not sure why I replied here. I guess I'm saying that establishing some kind of mesh network protocol between all cellphones would be a great addition to those other protocols you mentioned.)

Cellular modems are typically locked down completely to shit. But I know of a few LTE chips that can be obtained with no pre-burned vendor boot keys, and also have the vendor modem sources and toolchains leaked.