There is LoRaWAN with tech like Meshtastic which can send messages far further than wifi and bluetooth. Problem is the throughput is pretty limited. Only really useful for text messages within the same city.

Not sure any purely wireless system would scale that well either since every message floods the entire network. Ideally for wireless you just want wireless to the closest grid connected node to connect to the internet.

An app, in an official app store no less, is not going to be a solution for long. If you want an actual technical attempt at a solution you first need to regain ownership over your computing devices.