A few years ago I saw a video about some work at some university, might have been MIT, where they could figure out somebody's heartrate with some software and a video of their skin. It would look at the subtle flush of red every time the blood pumped past it. They had taken some footage and artificially magnified yhe flushing to demonstrate it, and they had done that with a few movie scenes to show how the actor's heart was beating while the scene was being filmed. I can't seem to find it now though, anyone remember any more details about it?