Many fitness apps are designed to be used in conjunction with smartwatches, and take advantage of the watch's sensors and features to track fitness data and offer additional features.
For example, many popular fitness apps, such as Strava, MyFitnessPal, Endomondo, Runkeeper, and MapMyRun, offer smartwatch companion apps that allow users to track their workouts, view progress, and receive notifications directly on their smartwatch. These apps can track steps, distance, heart rate, calories, and other metrics. Some of them also provide GPS tracking to track your runs or bike rides.
Other apps such as Motion allow users to not only track their weekly activity but also receive smart goals. Motion collects the users' historic activity data from their smartwatches and finds their average week. With this, the app sets the user the goal of beating their average week in order to make progress.
Additionally, many smartwatches such as the Apple Watch and Samsung Galaxy Watch also have their own built-in fitness tracking features and apps, such as the Workout app on Apple Watch or Samsung Health on the Galaxy Watch.
In general, fitness apps that work with smartwatches can be a great way to keep track of your fitness progress and stay motivated, since the data is easily accessible and the apps are convenient to use.