A Google+ post by Timothy Jordan (Senior Developer Advocate at Google) highlighted how any app that serves notifications on your Android smartphone or tablet can be extended to show notifications on a wearable device running Android Wear with minimal effort.
The examples shown in the blog post can be seen below and include a warning from a Nest thermostat, a calendar notification, a message from the Clash of Clans mobile game and the StarShipSofa science-fiction podcast being played.
The origin of each notification is identified by an icon in the top right corner, or by a background image.
Jordan also mentioned that by adding a few lines of code, developers can “deliver even richer experiences on the wearable by using stacks, pages and voice replies.”
The notifications themselves seem to take up the lower half of the screen, with Google also recently demoing a right-to-left swipe gesture that allows you to view longer notifications over multiple screens.