As any cat owner knows, our feline friends spend an inordinate amount of time watching (read: plotting against) us. So I suppose it was only a matter of time before we adapted our surveillance mechanisms to watch them back.

After years of watching a neighborhood cat prowl around his yard, Arkaitz Garro, a front end engineer for WeTransfer in the Netherlands, decided to investigate whether it was a stray. He told me he and his wife “became friends” with the cat and later learned that the cat—whose name is Bobis—wasn’t a stray, but actually belonged to their neighbor.

“Bobis has developed a schedule where he comes to our house at specific times and so we wanted to be notified when he was around so we could open the back door for him,” Garro told me in an email.

So Garro set out to develop a cat facial recognition system as a literal ‘pet project’ for Bobis. According to Garro, the device is made from a small camera and a Raspberry Pi running motion detection software.

When the camera senses movement, it takes a photo and sends the photo to AWS Rekognition, a free cloud-based image recognition platform. Rekognition then compares the photo taken by the computer to other photos of the cat that were uploaded to the cloud by Garro. If it matches, Garro receives an alert on Slack letting him know that there’s a cat outside that wants to come in.

Bobis waiting in front of Garro's facial recognition system. Image: Arkaitz Garro

According to Garro, the whole setup only costs around $50 and took him a few hours to put together.

“It’s almost one hundred percent reliable when the cat is looking at the camera,” Garro said.

If Garro’s pet facial recognition software is too DIY for your tastes, however, you can always build a pet facial recognition device that was developed by Microsoft. Released late last year, the DIY IoT device hooks up to your pet door to only allow animals you choose access through the door. If the facial recognition tech determines the animal is a match, they are allowed to pass through.