I have an engineering friend used a facial recognition system with some tweaks. Apparently you can download pre-existing code for the Raspberry Pi.

So what did my friend do with it? He painted a bad guy blue!!!! You see he, had a string of vandalisms that were specifically directed at him like wires and water lines cut. My friend decided to repurpose an air operated potato cannon to paint the perp blue. He was afraid that he would get into trouble if he painted a dog, cat, mailman, or child. So he used the raspberry Pi equipped with a camera and facial recognition software to prevent mistakes.

He set up a bait (cheap lawn ornament) that he rigged the ornament so it was difficult to remove and ran a trigger wire. The raspberry Pi prevented false firing. The potato cannon was filled with blue dye that you use in your washing machine to permanently dye clothes. The dye was mixed with shampoo and other ingredients. The cannon was hidden in a rosebush. One day he saw that he had a blue lawn and ran to check out the video record. He was definitely successful painting the bad guy blue. He also got video footage of the bad guy getting into the his car and driving away along with the license plate. The cops were called and the bad guy picked up.

Turns out that the reason was the bad guy had beef with the previous owner and didn't realize that they had moved and a very smart engineer moved in. Hahahahaha... He never pressed charges as the bad guy was a really bad guy that was wanted by the police and apparently discovered other things he was doing that put him away for a very long time.

@themarkymark, I Resteemed your article!