The app lets you draw, color with your finger and comes as a free app with in-app purchase of additional brushes, pencil, marker. Recently they announced pencil, a Bluetooth stylus that comes in graphite or wood to help illustrator to add a new level of creativity with the app. The device mimicking a real experience of drawing on paper with the capability of distinguishing the resting palm or the tip of pencil touching the surface with sensitivity. The other end of the pencil is the eraser. Of course, finger can still be used for smudging the water color
A new version of the Paper app has been released to support the Pencil. You can purchase Pencil HERE the wood version costs $60 and the graphite version costs $50.