I just stumbled across this great site. The owners of two mouse-happy cats wanted to prevent them from bringing them in the house, so they hacked an image recognition system onto a commercially available cat door that would compare the profile images of cats trying to re-enter the house to known features of their two cats. If the cat is carrying something in its mouth, the door remains closed. If the cat is mouse-free, the door opens.
They don’t say if the two cats ever worked together to defeat the system, but they do show an image of a skunk (black-hat hackers that they are) rattling the knob to come in.
It would be really cool if the source code was available.