That is exactly why I put a pcProx Sonar and that foot-implant-operated RFID reader under my desk (and I plan on sticking one in my desk chair too): the sonar locks my session as soon as I leave my desk, and the RFID reader (foot or butt) makes logging back in seamless.
I leave my desk like 30 times a day, and the forgot-to-lock-the-session jokes get tiring fast - and the logging back in too, if the session is locked. Hence… RFID to the rescue.
At least a Hasselhoff image (or Rick Astley or whatever) is mildly funny. My stupid coworkers invert the display (messing up the desktop icons) or send lewd emails with your account…