All these Wifi for tracking people methods use the channel state information (CSI) that is used to help decode the transmitted data. CSI is obtained from pilot signals that are transmitted as part of a regular transmission. This is done in basically all digital communication standards, so you could do this not just with Wifi but also with 4G or 5G or older mobile communication standards. This is all not very surprising, there is a lot of research in contactless radio based heart rate monitoring, they usually build on radar systems not communication systems though. The buzzword for 6G for all this is joint communication and sensing.
All these Wifi for tracking people methods use the channel state information (CSI) that is used to help decode the transmitted data. CSI is obtained from pilot signals that are transmitted as part of a regular transmission. This is done in basically all digital communication standards, so you could do this not just with Wifi but also with 4G or 5G or older mobile communication standards. This is all not very surprising, there is a lot of research in contactless radio based heart rate monitoring, they usually build on radar systems not communication systems though. The buzzword for 6G for all this is joint communication and sensing.