It seems that Google has recently made some changes to the Play Store where it will now display icons to show that an app has been designed, or at least has a version for Android Wear. As you can see in the screenshots above, apps that do have such support will display a small watch icon and the tagline that states that it has been enhanced for Android Wear.
However it should be noted that not all apps are displaying that icon yet. For example Google’s apps, most of which support Android Wear, currently do not display that icon but that doesn’t mean that they do not support the platform. However we expect that they will be eventually updated with the icon so you will want to keep an eye out for them.
Apple has something similar with the Apple Watch where within the app, they will also display whether or not that app has a version designed for Apple’s wearable.