I don't have security cameras in my house but that's actually interesting to see how things most people have in their house can (and does?) used to spy on them.

Phones and smart TVs, probably other appliances. My SO used to be surprised to receive ads about stuff we talked about minutes before. I finally looked at her phone, disabled a bunch of things in the stock Android settings, those timely ads went away. I didn't even have to install Blockada, uBO for FF (and uMatrix and other addons) like I do on my devices.