They watch you through your electronic devices that connect to your wifi. Your router are belongs to them, every electronic device, e-mail account, and website you visit is tracking you. They have density maps of places you go, words you say, psychological profile, average speed you travel, average distance, where you spend your money. Your whole life is Truman Show'ed to anyone that pays. We already know, and we also know how the system isn't perfect and makes a lot of mistakes like self driving cars.