If you exercise periodically and don’t have a cardiograph to check your heart rate, the Cardiograph Android app will help give you an idea of what your heart rate is at any given time.
This tool works using your device's flash, which you have to put your finger over so your pulse can be calculated. After the few seconds it takes Cardiograph to detect your pulse, your heartbeats per minute will appear on the screen, and you can view how they increase or decrease according to your activity.
Once you've taken your heart rate, you can add the entry to your registry so you can see how your heart responds to different exercise intensities and plan your future activities without pushing your heart to the limit.
Cardiograph comes with the option to create multiple profiles so several people can use it on the same device, so you can go running with friends or family members and keep track of everyone's heart rates using different accounts.