How can I control lights on a 3-way circuit with a timer?
How about a light switch with a motion sensor? They make ones that are occupancy detectors (detecting motion and then turning on), and vacancy sensors (detecting absence of motion and then turning off). They'll also have a button which can manually toggle the light on or off, and you can set the sensitivity and how long an absence is required before the light turns off. California Title 24 now requires vacancy sensors in many indoor areas; try looking for switches which comply with that.