Layer (http://layer.com) is building a successor to XMPP that's optimized for mobile and solves device coordination problems. The inventor of XMPP, Jeremy Miller, works there.
This looks interesting. I looked at their site and documentation for implementing a client (once they are up and running). Do they provide any other information about their goals? Do you know if they have a goal to let anyone run a Layer server with interopability like xmpp does?