The popular ski and snowboard app Slopes added support for Apple Watch Ultra’s Action Button in a version update last weekend. It's also one of the few third-party apps that can natively support the feature.
Apple Watch Ultra users can program the Action Button to directly open the Slopes app to start skiing or snowboarding training faster. After the user clicks the Action Button, it can automatically open the Slopes application, automatically determine the location of your resort or off-road area and start exercising.
The number of third-party applications that currently support the Action Button is very limited, and even popular applications such as Strava are not supported. Users can customize the Action Button through the Apple Watch Ultra Settings app, which supports shortcuts to start a workout, start a stopwatch, add a waypoint to the compass app, start a dive, activate a flashlight, and more.