Build by the Angry Robot Zombie Factory.
Harmonious is based on Harmony by Mr.doob licenced under the MIT licence. It was built using Phonegap, jQTouch and the Glyphish iPhone icons. All of which are fairly excellent.
If you like this, you should buy the full version from the iTunes App store. The full version lets you save your drawings to your phone and upload them to the Harmonious gallery.
Tap with two fingers to erase the last few strokes but still leave the impression – just like a real sketchpad.