The Google Fit app tracks heart rate periodically throughout the day. The Moto 360 3rd Generation Smartwatch used the Google Fit app to monitor heart rate.
Also, there are 3rd party apps, such as the Cardiogram, which you can download to give you a more in-depth look at heart rate results. You can use this link to download the app: https://play.google.com/store/apps/details?id=com.cardiogram.v1.
Unfortunately, the device does not support the detection of atrial fibrillation.
