Tracking Physical Activities

A question was posed here about tracking meetings, but I thought I'd expand upon that. I'd love to see the ability to track physical activities. One way this could work is by bringing up a dialog after a configurable period of idleness. When the user returns this dialog could ask if they would like to track any of the time spent away from their desk. They could assign an activity to this time, enter a brief description, and choose an amount of time to attribute to the activity. That would be great to cover things like research (with books!), manual work (physical mockups, etc.), and of course, meetings.