You are munging several issues here, but the biggest one is Jerry has already written such a script (I think) or has figured out how to, and the next release of Links with the updated user registration features should make that easy to do. Just query the sessions database for transactions less than 10 minutes.

Remember, being "on" the webserver is not quite like being "on" a bbs. you are not really "attached" to it, and you may be "logged in" yet be on some other site and not coming back.

It's only an approximation based on past (or current) activity on that server.

http://www.postcards.com
FAQ: http://www.postcards.com/FAQ/LinkSQL/