I have a customer that wants to allow only one user to logon at a time.  Are there any login modules that do that?  Basically check if the user is logged on and not allow another login.  Or at least kil the session for the existing user.  They want to limit password sharing on their site.

I'm aware of the issues of a user being offline but the system still thiking they are on until a session dies, and thus, not allowing anyone on for a few minutes.

Probably the best option is one that checks if there is a session, then asks if they want to kill the existing.  Nonetheless, does anyone have an idea how to do this or if a module exists?  Thanks.

Dax