Suggestion: Users Online
I wanted to bring this up again in the hopes that we can get a bounty going for a potential developer for a new chat system.
It seems the real difficulty is actually finding someone with the time to do it but money seems to be a nice motivator and I know a few, myself included, would donate to the cause.
I did a little searching and I found a few pieces that match what we are looking for (as far as my mind can tell) and while they may not explicitly work perhaps the code in the first one can be of help.
nodejs and websocket simple chat tutorial
An already existing messaging client could be implemented as an alternative such as Google Hangouts but then you are subject to a number of issues such as privacy and regional availability.