I've built something along this line, which I'm hoping to launch in the next few weeks.

It's not done yet, but what ever is? ;)

It works by building a system of distributed identity and messages around GPG signed JSON, and can be distributed over any medium. Right now, It's web-based and HTTPS calls, but I'm actively looking for a good webrtc solution I can use without leaking users IPs and other data.

There's some information about it at Tavern.com

If anyone's interested, I'd love to work with you to figure out how to make it better ;)