The Heartwatch app is the best workout & fitness app for Apple Watch, allowing you to get a very detailed, visual look at heart rate data. The Heartwatch app and its companion iPhone app are the best workout and fitness app for Apple Watch for someone that cares about their overall health.
The Apple Watch comes with several fitness features that can make your workouts more efficient and effective. These features include the Activity app, which turns daily activity metrics into long-term trends, GPS, and Heart rate sensors. It also comes with Activity rings which help you measure your heart rate while you exercise.