MotionCAPTCHA is a jQuery CAPTCHA plugin that requires users to sketch the shape they see in the canvas in order to submit a form.
It’s based on the HTML5 Canvas Harmony drawing tool by Mr Doob and the $1 Gesture Recognizer algorithm by Jacob Wobbrock, PhD and Andrew Wilson, PhD (and more on the recent Protractor improvement by Yang Li, PhD).
At the moment, it’s just a proof-of-concept, (no IE8 support) but the next releases will see progressive enhancement and the ability to use this in production environments as a serious CAPTCHA alternative.