Heart Rate Free - How it works I have received several inquiries about my heart rate app and decided to share details about it. The app uses your phone's camera to perceive the faint changes in the light coming off the flash as blood flows in and out of your finger. I have also provided the demo code and some sample code segments to explain specific functions of the app and the augmented reality blog post for modifications. After a detailed explanation of the code, I show graphical presentations of how the app tracks heartbeats. I end off with a preview image of the sample project and... 25 November 2010