I think the point he is trying to make is that this tool seems to make it easier to the point he is willing to put in the effort/time.
Exactly. Minus the job and kids, I'd love to have the time to learn all the tools I need for all the dozens of projects in my head. But if this makes it easier, it greatly increases the chance of the project actually happening. (And heck, I still have to work out how I'll actually send the signal to the servo...)
You only need something like 30 lines of code to do it with openCV
Unless you have some feature detection for cats, I don't see how you can discern whether it is a cat or someone's arm.