If you question yourself why move to an Erlang RTP Proxy if you are using openSER, Asterisk, or any other SIP based service. I can also say that the benefits don't seen so clear too.
But it turns out to be coolest solution for Jingle Raw-UDP Proxies! As you can integrate with your EJabberd as a module.
Check http://code.google.com/p/erlrtpproxy/ for the RTP Proxy application.
I've developed several RTP Proxy based on XMPP for the last few years, including Openfire RTP Bridge, which is pure Java and embed in all Openfire deploys.
Stay tuned! I will publish the RTP Proxy Module for EJabberd soon!
But I can give you a hint that this one looks specially promising: