When you work out in the gym, you can actually see the heart rate (the rate at which your heart is beating in beats per minute or bpm) in the equipment itself. On the other hand when you are running outside or doing push ups at home, you cannot really find out the heart rate without buying some expensive health or fitness gadgets. But if you own any standard smartphone running on Android OS and having a medium level camera with LED flash, then you can use it to calculate your heart rate at any instant you want using the free Heart Rate app.
The Heart Rate can use your camera along with the LED flash to see the change in the color of your fingers as the heart pumps the blood to them and using this information can determine your heart pulse rate to a certain degree of accuracy. So after you have installed this app in your phone, you can touch on Get Started and then put one of your fingers on the camera lens. It will take a few seconds before it will show you your current heart rate in bpm.
As you can guess the heart rate changes from one instant to another, so the app keeps calculating and re-calculating the heart rate every 15 seconds. My heart rate varied from 78 bpm when I was sitting still to 90 bpm when I started taking deep breaths rapidly. I suppose if I had run along the street and then checked, it would have gone higher.
The app also gives you useful information such as the target heart rate to keep your heart healthy and in shape. You can also upload the heart rate data calculate by the app to Google Fit so that it can be shared by other online services and apps.
Conclusion: Heart Rate app turns your Android smartphone into a simple heart pulse rate calculator device. All you have to do is put your finger on the camera of your phone and Heart Rate app will instantly show you your current heart rate.
You can get the Heart Rate app from https://play.google.com/store/apps/details?id=si.modula.android.instantheartrate.