By now, it should be clear to us that wearable apps cannot always follow the same UI patterns that their handheld counterparts might. Wearable devices have a significantly smaller form factor and interacting with them places heavier constraints on user actions. For this reason, the Android Wear user interface APIs are functionally divided into Suggest functions and Demand functions.

The Suggest functions are embodied by the Context stream—a stream of information presented in a manner that is proactive and suggestive. Users are shown a vertical list of informational cards, which can be scrolled through until the user wishes to interact with a specific card.

The Demand functions are reflected in the cue card metaphor. A cue card can be opened by saying OK Google, or, we can open it by tapping on the background of the home screen. Each voice command activates a type of voice intent, which in turn can be associated with multiple applications.

When presented with intent, the...