how can I make an Apple Watch workout app ?

To create an Apple Watch workout app, you can utilize WorkoutKit, which allows you to create and sync various types of workouts directly from your app to the Workout app on Apple Watch. Here are some steps and features you might consider:

1. Custom Workouts: You can build goal-based workouts with singular goals for energy, time, or distance. Additionally, you can create custom workouts with structured steps, including warm-up, work, recovery, and cool-down types. These steps can be grouped into repeatable interval blocks.

2. Custom Swimming Workouts: If your app caters to swimmers, you can build custom swimming workouts. WorkoutKit provides a new goal type that combines both distance and time, which is particularly useful for pool swimming workouts. You can also customize step names and use the workout scheduler API to schedule workouts.

3. User-Selectable Workout Locations: Starting in watchOS 10.1, you can allow users to select workout locations, such as indoor or outdoor, without specifying them in advance.

4. New Features in watchOS 11: With watchOS 11, you can customize the name of your workout steps and use the new distance with time goal type for custom workouts. This version also introduces enhancements for live activities and widgets on Apple Watch.

For more detailed guidance, you can refer to the session Build custom swimming workouts with WorkoutKit (04:20) from WWDC 2024, which covers the creation of custom swimming workouts and other enhancements in WorkoutKit.