I've also modified the Now Playing plugin for Canvas so it will clear the data when you pause the music. Now my Pebble displays the track info while music is playing, otherwise it displays the calendar. My modified Now Playing plugin is on github: https://github.com/c99koder/CanvasNowPlaying
I built a simple calendar plugin for Canvas for Pebble. Source is on github: https://github.com/c99koder/PebbleCanvasCalendarPlugin I might make it available on the Google Play store after I've polished it up a bit more.