The brilliant Joe Dale @joedale sent these useful articles which will explain
the use of QR codes far better than I can.
http://www.slideshare.net/joedale/exploring-the-educational-potential-of-qr-codes
http://learninginhand.com/blog/learning-in-hand-25-qr-codes.html
http://joedale.typepad.com/integrating_ict_into_the_/2011/07/ipod-touch-training-in-mfl.html