Not yet. I just don't know where to put the button. :)
Discussion
It could be an option on the "new note" button.
Like *click* "new note?" "New chat?"
It would also be nice if the chat itself (not necessarily the messages) could stay in the messages list once you click the join button. That way you can easily resurrect old chats. Add it is that disappear from view, and return when there is activity.