In the days people used screensavers on computers I had one set to 30 minutes. Don't know why, because it was a bit too short time for me but anyway, that is how I did it. So sometimes watching a movie I had to remember to move the mouse sometime or screensaver would kick in. Then many times when I watched TV I felt the urge to move the nonexistent mouse.

Also I've gamed many times until I see the game afterwards for hours just closing my eyes.