This is very similar (but far better done) to something I did about 8 years ago for a client while I was working in Australia. The idea was they had a photo of a bedroom and they could draw on top of the image to isolate items in the room that could be purchased.

What I wrote was very very basic, but what you've done is far more impressive and awesome.

Edit: This is something I wouldn't block (from what I currently see) unless it attempted to know everything about me. Damn tracking.