If it's on company property and the workers are given notice that it's happening then I guess you can say it meets an ethical standard...that doesn't make it a good idea though, a great deal of time and effort will be spent trying to circumvent such tactics and good luck having your employees trust you after, if your employees are doing what they are supposed to do and meeting their expected performance, there's no other reason to surveil them except you're a mini fascist control freak

As long as your employees are producing the things you hired them to produce in the necessary time frames, then any form of surveillance seems extraneous. Even if someone if not producing, it seems more impactful as their manager/higher-up to have a conversation about what barriers they're facing rather than some creepy Panopticon surveillance system.

I think those automated, screenshots every 30 minutes to see if it's the same as the last one (and they are not in a meeting) and flags for human review if it's the same makes sense. As its not too taxing and not too surveillance heavy. But other than that I think to actively monitor people that hard is only going to piss off your workforce, likely break GDPR regulations and likely lead to a lot of false flags.

No.

I'm not sure how theoretical vs practical the principles of ethics are, but I think surveillance on employees may be theoretically okay - you're paying them to work, you "should" have the right to determine if they're actually doing their jobs - but not necessarily okay in practice - it's rather authoritarian/Orwellian and may compromise employee morale.