IANAL but these observations are all location related. The police don't need a warrant to follow you (I don't think). Isn't observation by tracking your phone a lot like that? A detective following you could also observe private details about your love life and your place of worship.
Yes, one detective can learn a lot about one person's life in a given timeframe by actively following them. That's different from X00,000 detectives who never sleep and can follow everyone, everywhere, constantly, at very low cost. People/agencies with access to these "detectives" can "retroactively follow" people, something not possible with the lone human detective. IMO there's a huge difference in both quantity and quality of this tracking.
