You can already use a browser, email client, and video player on Android Wear thanks to Appfour, and now you can check your calendar too. This dev specializes (apparently) in taking full-size apps and shoehorning them into the small form factor provided by Android Wear. Sometimes it's a bad idea, but it's at least good for a laugh. This one seems somewhat useful, though.
The main view of your calendar in this app is a full month, which doesn't show you much. At most you see a few letters of a single event, but swiping over gets you different layouts with more detail. You can tap on a day to zoom in and see events more clearly. Adding events is handled with another tap. You can enter details by voice, or with Appfour's trademark scrolling QWERTY keyboard. There's also a radial UI to select event times.
The app is free to use, but a $1.49 in-app purchase will unlock a number of features like adding/editing events and configurable layouts. That can make things easier to see on the small screen, so you might actually want to check your calendar on the watch. Unlike the Wear browser, I can actually see this one being useful to some folks.