Pebble Watch Pro by Greg Banta in an unofficial app to use with your Pebble watch that allows users to receive Calendar, Twitter, Battery and Network alerts right on your wrist.
In addition you can control music on your Windows Phone right from the Pebble. Select songs from Playlist, Genre or All songs on your phone and then pause/play move to the next or previous song right from the music app on your Pebble.
The developer also has a free app, Pebble Watch Lite, which only includes the music feature.
The app costs $1.99, unfortunately without a free trial, and can be found in the Windows Phone Store here.
Read more about the apps at BadPlanetSoftware here.