My devices are not open to public use, so it's likely you would have to significantly invade my privacy to do that. There's no expectation that you are allowed

My devices are not open to public use, so it's likely you would have to significantly invade my privacy to do that. There's no expectation that you are allowed to do any computing on my devices. You're already allowed to browse the internet, use Facetime, take pictures, etc. on the computers in an Apple store so the line where inappropriate use begins is a lot less clearly defined. Would a Facetime call made from an Apple Store computer that captured the faces of people walking through the store behind you be offensive or illegal? I don't think so, so where exactly is the line? Capturing a singular moment in a person's life in a fixed context is also significantly different to me than capturing the entire story of their public life. What you are proposing has a tracking component that the OP's project did not, so I don't see it as an apples to apples comparison. I don't think people should generally face punishment for taking pictures in public, and if you took my picture each time I went to a particular store without stalking or harassing me, and without using the pictures for malicious purposes it's hard for me to see that as criminal or particularly wrong even if it's not entirely comfortable. At the very least it's a common and legal practice for stores to do so via their security systems, so I'm reluctant to villainize art that points that surveillance out as opposed to the actual surveillance itself. To be clear, I'm not saying that installing spyware can't rise to the level of being wrong or illegal, I just don't see this example as very egregious. Your example would be much more insidious.