Good point. I didn't really explain how this was specific to the raspberry pi.

There are a bunch of off-the-shelf solutions, but they are overkill if you're looking to do it yourself. Many of the "turn-key" products send an HD stream with audio to a server, which utilizes a bunch of bandwidth. I don't really like that idea, even if my internet wasn't metered.

These scripts are optimized for the pi zero hardware. Instead of capturing a 4MB image by default, which takes 30 seconds to compare, this solution captures a 150k image. That way I can get it to compare images once every 3 seconds or so.