Resto Shaman Mastery
The addon records all heals cast during combat and the estimated effect of mastery on the respective heal. At the end of combat, the addon prints out the weighted average of the effect mastery had on your heals and resets the counters. You can additionally print out the current results and reset the data mid-fight by typing /rsm into the chatpane.
Development has been moved to http://www.curse.com/addons/wow/restoshamanstats