2 days
I frankly think there should be something like a Bluetooth-based protocol allowing for every messaging app to exchange messages, much like #XMPP. Then, even if you block one app, there will be others available that anyone can use with the people that managed to install that blocked app in the 1st place.
I’m also thinking about the possibility of blocking/hijacking the network by the law enforcement forces. If every device is also a node connecting to each other, they can be more hardly taken down I think.
I’m not so familiar with meshtastic, but wouldn’t be more helpful to have something that actually runs on people’s phones instead of having a separate device? I mean, as you said, everyone has phones, and with something like the Ripple app (or any other panic button app) you could hide the app or clear its data (or you could do it manually). With meshtastic, in the event of a search, I think you would be more suspicious, I think.