Wristlevels
Uses WatchKit to let the user control their Sonos system from their Apple Watch. Users can adjust the volume with the Digital Crown, tap Vol-/Vol+/Mute buttons, or directly input their desired volume with a number pad.
WatchKit is a framework that allows developers to build, customize, and manage user interfaces and interactions for apps running on Apple Watch.
I’ve used WatchKit on two of my projects: Wristlevels and Breathanchor. Breathanchor works as a standalone app on Apple Watch, while Wristlevels uses the iPhone to authorize your Sonos account. Both apps make use of the Digital Crown to adjust and interact with the app.