User Session Active?

[BPetro]

Has anyone done work to keep a 'heartbeat' to know that a user is still around? I'm thinking I can popup a small window that can sit in the background or be useful for other purposes and have that window do automatic refreshes which get passed on to a database lastHeartbeatDateTime field. Each user is logged in so we know who 'owns' the session.

Any other ideas? Any better way? The big picture would be to display a list of co-members who are actively online. Any ideas of the best way to do this?

Thanks!