Hidden cameras are simply scary.

Sight is a great short film sharing the anxiety of the times (also must see Charlie Brooker's Black Mirror)
For me the interesting thing is seeing the fear of covert surveillance  becoming more and more intimate as it becomes more plausible. It makes you wonder at what point society will require conspicuous technology.

From aliens watching us (War of The Worlds, Invaders,) then governments (1984, [any spy film ever]), then local law enforcement (Minority Report),  entertainment (Truman Show), of course on to CCTV society, and reality TV (Big Brother) covert observation has always fascinated us. Right into fetish territory of the voyeur, watching and being watched . 
And now as that technology becomes intimate we increasingly perceive how we will covertly surveil and interact with each other (Black Mirror, Augmented Cities, Sight). 
It's interesting. It also generally overlooks just how boring our lives are. (although Sight does quite a good job of emphasising that. Not quite sure why a blank wall is worse than an Xbox, but there you go).


Ultimately this film is scary because when something becomes entirely concealed, we can only imagine, and our imagination is the scariest place in the world.
  


It is rarer to see elegant visions of unobtrusive technology actually augmenting reality. I suppose more like BERG's "incidental media" which is about train tickets instead of stalking. 


(also , pedantically)
Slightly frustrating to see augmented reality projection-mapped without the multiple camera's, audio, gyros or accelerometers required - but that's sci-fi I guess. It's all about hidden cameras.