21 Day Advantage is my pet project.
One of the most influential videos in my life has been Shawn Achor's The happy secret to better work. In the video, Achor outlines 5 steps to repeat daily for 21 days, that will positively affect the way you view the world.
I made a Windows Phone 8 app to help myself follow the 5 steps, and one of the high points was being featured on the Windows Phone 8 Store! It is now down due to my lack of a Windows Mobile 10 device, but I am currently in the process of making an Android version.