Now all this needs is a few good third party audits, verifiable builds and it's the holy grail of encrypted communications!
Torsten Grote, one of the projects main developers, explains the technology behind it in this very nice presentation: https://m.youtube.com/watch?v=Dr42vZIoGqM
The ability of TOR to allow essentially roaming services like this is a feature I'm always surprised isn't used more often. And although it's not something I was ever going to actually get around to, something like Briar has been on my list of interesting thins to try to do for a while -- I'm really glad someone else has had a similar thought and been able to run with it :).