This application will allow you to check your heart rate.

It works by analyzing video feed of your finger placed over the camera
objective, with flash enabled. We can then detect slight red channel
color changes that occurs when heart beats.  With simple derivative
computation and some heuristic to avoid false positive, we can then
count beats and thus heart rate.

Please note this has only been tested on FirefoxOS running on Nexus S,
and while it gives good results, it is not expected to be medically
accurate.

Also, to make it work, it relied on several bugs:
 - https://bugzilla.mozilla.org/show_bug.cgi?id=787812, to add Nexus S
   pixel format to allow copying frames from video to canvas
 - https://bugzilla.mozilla.org/show_bug.cgi?id=832745, to be able to
   copy frames from video camera feed to canvas
 - https://bugzilla.mozilla.org/show_bug.cgi?id=825325, to get
   mozPaintedFrames values