Secret Code Idioms targets 24 different common idioms. These idioms are presented three different ways:
Pages 3-8: idiom presented with QR code answer
Pages 9-14: idiom presented with a choice of three answers and a QR code answer
Pages 15-20: Worksheet with space to write the meanings of the idioms. QR code answers provided on the worksheet to make it self-checking.
You can see more of this product at my blog: speechuniverse.blogspot.com in the March 2013 archieves.