Wi-Fi allows you to see through walls.
If there is a cup of coffee on the table, you can see that there is a small object on the table, but it will not be possible to recognize it because of the indistinguishable shape.
xxx: But you can identify a person or, for example, a dog, and in fact, any object larger than four centimeters.
yyy: In life, the technique would be useful for law enforcement, for example, when seizing an institution with hostages.
ZZZ: Or the housekeepers. Check the presence of residents, dogs, neighbors before moving the apartment.