This video for the song named "Undivided" by the band Blush is intriguing. First of all, because it's a pretty solid pop song (with, as far as I can tell, a rare safe-for-work appearance by Snoop Dogg himself). Second, because the simple but beautiful animation was entirely created by animator Shawn Harris on his iPad using the Brushes app.
It's very well done. You can tell that many of the parts are strictly done with finger painting, but he's also got some interesting photo editing effects, too. There's a "making of" video to watch as well that goes through some of the techniques used by Harris. Surprisingly, it was all done in the app -- he simply recorded each brushstroke as a frame of video, and used Brushes' own tools to output the final product. Good stuff!