Dave Young wanted to stop his dog from jumping up and taking food off the kitchen work surfaces (I can sympathise!) when he wasn’t in the room. So, he hooked up a laser detector circuit to a Raspberry Pi and programmed the Pi to play a recording of his voice to tell the dog off when the laser beam is broken. The recordings are randomised so that the dog doesn’t keep hearing the same thing and a photo is taken using a camera module. Read more here, including full instructions. You can see a video of Dave explaining his project and an example of the dog misbehaving below: