secure smart lock. A house owner with hidden security cameras in the living room will most likely not disclose them to you, but the messaging history will serve as proof if they do get caught red-handed.
The network scanner Home Guard will display which devices are security cameras and what are their vulnerabilities (such as open ports). In the Irish Airbnb home, it was precisely an open port that allowed the guest to break into the camera and access the video stream. Surveillance cameras can be notoriously insecure, which means that your host might not be the only one watching your every move. A network is as secure as its weakest link in the chain. We would never advise breaking into an IP camera that is not your own, though. 🙂
Relaxing on your holiday should not mean also relaxing your privacy standards. With a few precautions, your only concern on your days off may be whether you need to pack an umbrella or not.