Pendulum for Gear is a calendaring application for your watch. It allows you to read events on your watch, create events on your watch, and even manage tasks.
Pendulum also pulls in events from other calendars that are available on your phone (note that its current behavior is to pull in events from all calendars).
Pendulum has an on-watch keyboard interface, but also allows you create events quickly (with a dropdown) if needed.
It also contains a todo list. This allows you to create tasks on your watch, view them, and and mark them as completed.
Note that events you create on your watch might not yet sync as often as you'd like (this feature is currently experimental). Also, in order to allow your events to save to the cloud, you need to occasionally open the application on your phone.
Also note that events are shown within your watch's timezone. This means that events created in calendars owned in another timezone might show up differently on your phone. A later version will more explicitly show the timezone distinction.