Smyrno was intended to be a Jabber client for Emacs.
Unfortunately, as with many of my other half-finished projects, I will likely never get it up to speed to be actually useful as such.
Low-level prerequisites for an Elisp XMPP implementation (SAX-like XML parsing and XML Streams support) which were implemented for Smyrno can be found here:
These are a good, solid foundation on which further Emacs Jabber work can be done.
I’m attempting to refactor ERC enough such that it can use XMPP as an alternate backend protocol, but I make no guarantees that it will ever be usable as such, or that I’ll ever have anything to check into ERC on this front. (Actually, to be honest I ran out of steam working on Smyrno because I didn’t feel like reinventing all of the wonderful UI work that ERC embodies, so perhaps I’ll eventually get somewhere with this.)