A free app for Android, by King Brain Inc..

This is an app that provides users with a quick, easy, and accurate way to measure their heart rate. It is designed for people of all ages and it is very simple to use. 

To get the best results, make sure that you are doing the test properly. The first thing you need to do is to make sure that you are still and not moving. Next, you need to place your index finger on the back of the camera lens. After that, you need to stay still for about 7 to 10 seconds.

The heart rate will be shown after a few seconds. You can check and see if the results are accurate.

The app has a built-in database of heart rates for different age groups.