Using Tasker with the AutoPebble and AutoShare plugins, I can access and play any of my Google Play Music playlists. Once I plug in my headphones tasker queries the playlists from GPM and loads them into a list on my Pebble. From there, I select a playlist and it begins to play! I also create a new playlist called "new list" and when I run the task again (plug in my headphones) the list is updated to reflect the changes.