A free app for Android, by Health Tools.

This application is used for heart rate monitoring, which may be useful during exercise, when you are stressed or if you suffer to heart diseases. 

It is also useful to get an estimate of your heart rate, whenever you need.

The app is based on the built-in sensors and devices (camera, LED flashlight, etc.) and calculates the pulse rate using the built-in function.

It is very easy to use. Just press the Start button, and then hold your finger on the camera lens. After that, you will see a number on the screen, which may be used for further measurements.