This is nothing new. Wifi signals have been used to detect objects, people and animals, gait analysis[1], read keystrokes[2], monitor breathing and heart rates[3], "hear" conversations[4], etc for at least a decade now.
https://news.ycombinator.com/item?id=12353605
https://www.theatlantic.com/technology/archive/2016/08/wi-fi...
1: https://ieeexplore.ieee.org/document/7457075
replies(3):