Ring (Beta Test) allows to make audio or video calls, and to send messages, safely and freely, in confidence. Powered by Savoir-faire Linux, Ring is a open source software that requires no central server.

What can you do with Ring:
  - make audio calls 
  - send text messages
  - make video calls (experimental support)
  - use your existing SIP account

Ring is in beta. There are plenty of ways to help us, check out: https://ring.cx/en/contribute

You can also install Ring on Windows, Mac OS X and GNU/Linux.

All the info is on https://ring.cx/en