I always liked the look of Briar but could never get enough people to try it out - it uses Bluetooth mesh networking but also allows for two devices connected to the same WiFi network to connect - this seemed like a sensible option because Bluetooth is too limited in the real world and would require everyone running it in the area around you. From the sounds of it, Bitchat being limited to just Bluetooth isn't going to work in its current state. It's still a great idea.