In many countries installing anything on any device of a 3rd party without permission is a crime.
It's also illegal to track location without permission or warrant. (They were thinking of GPS or other bugs on a vehicle).
So not just the people installing the wares Stalking companies, but Google, Microsoft, Facebook, etc may be breaking national laws in many countries. It's illegal for an employer too, without saying, even if the employer's phone, tablet, laptop etc, in many countries.