I have a sneaking suspicion that if you are a knowledge worker you are already probably doing this unconciously. Online research, entertainment and shopping for non-work related stuff, errands, stock trading, etc. Working from home makes this easier because you can have a non-work computer right next to your work laptop so no chance of the company snooping into what you are doing.

Ofcourse if you work where every hour counts- construction, nursing, waitressing, driving for uber- it'll be a while till people figure out they need to be paid more or work less for the same $