Earlier quoted context omitted.
100% agree. Relatedly, does a landlord have the right to know when you are in your home? Because that's a side effect of this (which could already be possible by monitoring things like electrical usage). Asking in both legal and ethical senses (which I expect are different).
Nothing to prevent owner of a building (landlord or other person/entity) from installing a camera and taking a picture of everyone entering the building (outside the door). [1] Inside (legally) maybe the same no expectation or privacy in the lobby of a public building. The end result of the landlord knowing when you are in your home does not change that. [1] Same principle that allows you to photograph the police out…
If you have a camera that has any publicly available (not just public, also private-but-unfenced) place in it's FoV, you must register with your local data protection office and fullfill all the requirements (you must prove, how you use, make available, securely store and dispose any recordings).
If you don't have any publicly available space in your FoV, you must have a written permission from all the co-owners (e.g. in an apartment house).
So basically it is only easy if you are sole owner of the property and only you (and your family) are using it. Anywhere with a shared space, it is an issue. For a landlord, that would get no-go quickly.