The ToF sensor is a great unknown in the smartphone world. In fact, since the Xiaomi Mi 9, the vast majority of Xiaomi smartphones integrate a depth sensor that has more possibilities beyond performing a better portrait mode.
A common sensor in mobiles with unexpected uses
Many Airbnb rental apartments have hidden microphones and cameras and record privacy of the user who has rented the house. Taking the above into account, several researchers from the National University of Singapore and Yonsei University have worked on a system to detect these cameras through ToF sensors (Time of flight) present on our mobiles.
In the end, these types of sensors are responsible for sending and receiving an infrared wave, in such a way that they can determine the depth of the objects. In fact, researchers have gone further and been able to develop a system called LAPD capable of recognizing reflections from camera lenses.
This system has a system of machine learning that is in charge of learning to be more and more precise. The tests give you 89.9% affinity.
Keep in mind that despite the fact that it is a technology based on the ToF sensor of your smartphone, nowadays there is no app that is capable of accurately recognizing hidden cameras or microphones.
Fortunately, there are other ways to know if there are hidden cameras or microphones where you are and it is through WiFi. The internet connection is essential to be able to receive the information, so another way to know if there are these devices in your accommodation is to identify those devices that are connected to the network.