Hi PF, I need some help. I'm studying to be an electrical engineer and i'm trying to make a cheap, non-invasive device that can detect when a person is starting to fall asleep. The device should be able to work on any person and perform a task before they can fall asleep. *Can anyone tell me what happens physiologically when a person starts to loose consciousness? As a bonus, it would be extra helpful if you know a way to easily and cheaply detect it. What I know: rapid eye movment- unusable beacuse the person is too far into sleep slowing heart rate- differs from person to person and is dependent on prior physical activity. unreliable? brain waves change- too invasive to detect and costly. Any more? Thoughts? Much thanks, Taylaron.