And what's great is that when you add someone as a contact, you become a potential mule for transferring encrypting messages they're sending to others contacts you've also added as a contact that are not in range.

This could be extremely valuable when the Internet access is cut off.

https://briarproject.org/how-it-works/

It’s fine for a building, a bar, a conference. But I really don’t think this is the app for a more distributed population.

It's working rather for small groups that actually have mutual interest, not random people from the internet. It has forums, blogs etc., I used similar project in a group of friends I know in person just to talk and share files directly and I was surprised how well received it was.