I built a game around this recognizer ("Magic Touch": https://www.youtube.com/watch?v=Ze9k0lseb-8 ). It's a very neat way to do shape recognition in real time. It's very well suited for mobile devices although it's far from being perfect. The interesting bit was to make the recognition lenient enough but still good enough to recognize the shapes accurately. Think about the difference between a 'V' and a 'U'. Anyway I would love to see more real world uses of this clever recognizer!