Camera Heart Rate Variability!

Camera Heart Rate Variability is the first and only app that lets you record, plot and export time and frequency domain Heart Rate Variability Features - without requiring any heart rate monitor. Camera HRV uses a technique called photoplethysmography (PPG for short), which consists in detecting changes in blood volume during a cardiac cycle, by illuminating the skin and measuring changes in light absorption. It should also work on iphones 4S (not 4) with iOS 8.0 or later.