You don't need to count seconds anymore or do any math in the heat of the moment.
Just by tapping your fingers to the pulse you feel, Vitals can calculate the beats per minute by detecting the subtle vibration changes via the accelerometer.
Even if your Apple Watch's screen dims, the second counter stays active and the app keeps detecting your finger taps.
Do you know the normal heart rate for a 7 year old child? No problem, just check the reference section in the app.