The Massachusetts Institute of Technology Media Lab has developed Cardiio, a mobile app, which can measure your heart rate within 3 beats per minute of a clinical pulse oximeter when performed at rest in a well-lit environment.
Cardiio works by simply having you look straight into the front camera of your iPhone 4S to measure your heart rate. Every time your heart beats, more blood is pumped into your face. This slight increase in blood volume causes more light to be absorbed, so less light is reflected from your face. Using sophisticated software, your iPhone’s front camera can track these tiny changes in reflected light that are not visible to the human eye and calculate your heart beat.
The app analyzes your heart rate data to provide you with a fitness level rating and also estimates your potential life expectancy. You can also set personal goals for your resting heart rate and see how you stack up against others.
The app costs $4.99 on iTunes.