Use the camera in your iPhone 4, 4s or 5 to measure your heart rate!
This app uses the camera and light on your iPhone to watch the amount of blood in your finger; by watching blood ebb and flow it can calculate your heart rate.
An on-screen monitor shows you your current heart pattern and rate — and the heart in the middle pumps at the same rate as your own heart!
You can store heart rates to review later and a full explanation of the science behind the program is included.