Sessions + logging in from only one location

[eluser]intractve[/eluser]
Plus points on your respect to someone trying to help.

The idea isn't "half-assed", it's a perfectly good idea. I have a similar setup running in more than 15 implementations of various apps I maintain.

Use database sessions and add a login_hash (a sha1 encoded random string in my case) and a corresponding login_hash in the user_login table.
When someone logs in I update the login hash in the user_login table and the corresponding session and then do a kick_others() that will delete any entries in the session table that do not have a corresponding hash in the user_login table. It's quite simple actually and I'm able to make it work quite well for me.