Wear OS smart watches already support AOD (Always on Display) or the screen is always active. But the support of this feature is very limited and unlike AOD on smartphones.
AOD on Wear OS only supports watch faces. If the watch face already has the AOD feature, a different design will be displayed that is dedicated to save battery and still be able to see the data in real time like the clock. But otherwise, the watch face just changes to black/white.
Not only that, if the clock face has data widgets such as weather, heart rate, total sites etc. – AOD rarely displays this data in real time because the clock needs to be activated first for the data to be refreshed. Recently, Google has updated the Google Maps application for Wear OS so that AOD support is displayed when using for turn-by-turn directions.
This allows the watch to display the intricacies of instructions without using high power and a lot of battery. Unfortunately, for now this support is only available on the Pixel Watch and there is no information if other Wear OS watches with OLED screens will also support it.