In a 30th May 2019 article at the IEEE Spectrum magazine web site,
MIT researcher Fadel Adib reports on his team's work on a low-power
household radar system that is sensitive enough to detect a person's
breathing and heart rate through the other side of a wall.
By making precise measurements and using machine learning, they also
claim they have demonstrated that they can even gauge a person's
emotional state to an impressive degree of accuracy.
How they did it here :-
https://spectrum.ieee.org/telecom/wi...-youre-feeling