Wow. Sounds interesting. I also looked for a solution to talk to relatives in case the internet gets blocked. Ended up with XMPP, since it has independent servers in different countries that can talk to each other. But the XMPP clients I tried are pretty bad, with no images or audio/video calls.

Did video calls work during the blackout too? I think calls should work like in the good old Skype days, pure P2P.