Hmmm - couldn't you simply use one of the available chats on vB.org? Simply set the settings so that only Moderators, SuperMods & Admins can view it

--- I'd recommend
Cyb Chatbox and you could put it on all pages of your forum. It would be a nice, FREE option that wouldn't be much of a resource hog since you'd only implement it for your Staff usergroups.
Jacquii.