Accessory makers Griffin have teamed up with everyone's favourite crayon brand Crayola for the latest entrant in their App Powered line. The Crayola ColorStudio HD pairs a digital stylus with a free iPad app, letting kids get creative on Apple's tablet without getting felt tip marks down the sofa, or worse; your slate's screen itself. But is the ColorStudio HD set any replacement for a colouring book and a cheap set of pencils?