>I need to add an auto logoff feature to an existing application. This is the standard "log off the user after x minutes of inactivity". I can think of several ways to implement this, but before I begin, I'm interested in hearing how others have done this.

While I've never done this, I'd just use a timer to check (via SystemParametersInfo()) if the screen saver was running. Not a lot of code overhead, plus you get a better idea of whether or not the user is actually doing something.