From: "Mohamed Magdy" <mohamed.m.k(a)gmail.com>
Subject: [Wikitech-l] Who is online?
Is it possible to have such a feature on Wikimedia
wikis? or it will not
be accurate and have the same problem of page views?
Try
http://www.mediawiki.org/wiki/Extension:CurrentUsers
I have not looked at it personally, so can't vouch for it, but it claims to
do what you want.
- Mark Clements (HappyDog)