That's pretty high risk on the host's part. If your guest happens to discover the camera and informs the police, at least where I live you would be looking at a

That's pretty high risk on the host's part. If your guest happens to discover the camera and informs the police, at least where I live you would be looking at a pretty hefty fine and possibly even a short prison term + felony criminal record. It doesn't help much if you are mostly spying on foreign tourist guests, since the act of visual spying of a private household is itself a serious crime - not only as a tort against a victim, but a criminal offence likely of interest to the public prosecutor.