Thanks thedaver. Must have been a post-good-coffee moment. I guess my post was a little vague however at the time it made perfect sense to me. Here are some more specifics.
If logged in to a session in run level 3 with no activity for a predefined period of time, the session will terminate and return the session to a log in prompt.
For XWindows/X11 a screensaver with a requirement for a password to continue working will meet the requirement. Also ssh sessions can be configured with parameters in the sshd config.
Thanks,
N