If you have an Iphone, an Android phone or a Mac, there is an app called Cardiograph that measures heartbeat rate via the inbuilt camera. You put the finger on the camera, the nearby flashlight lights your finger and then the color change of the pulsed finger is measured. As heartbeat meter it is ok, but unfortunately, it just exports PDF files with not very accurate ECG curves.

But you get the idea - you could program something similar using Processing and the Video library.