Hi.
Well, i've done it with the login module downloadable on my
site, which focuses on CBE. But the code orientates on the work of Richard Stupart
(
redferret.co.za ) and his mod_ajaxonline.
That module you can get under
mamboforge.net/projects/ajaxwhoisonline/
Just a note to be complete, ajax modules in the login area
should be used with care. joomla does not expire these
user sessions, as they are constantly reloaded.
On a "who's online"-module it has only the impact of a bit more open connections and datathrouput to / from your server. Depending on how your web daemon is configured you may be able to block it on sites with masses of online users.
Greets
Phil.