[Zope] Chat in CMF...

Does anybody know a chat tool for Zope? I know this one: http://www.zope.org/Members/jwashin/ZRTChat. But it is too simple because if users don't speak, you don't know whether they are online or not. If there are no more tools, could everybody tell me how can I detect, from Zope, which users are online? Is it possible? Thanks, Josef.