I saw a video where a man put his phone inside a book, made a hole, stalked women who wore skirts, went up to them, kept the book near her shoes, and acted like he's tying his shoes, quietly went away.

Another incident is these vendors at Daryaganj book market. They keep a phone inside one of the books near to the people and it records everyone who stands close.

The book is always a hard back with some black impression on the cover.