WiFi can also be used to detect heartrate and breathing, which can leak additional ad-targeting information related to activity, arousal, or agitation.
I am curious if, with the number and quality of signals they can capture from this, how uniquely they can identify individuals and determine things like age, gender, weight, etc. Particularly when analyzed probabalistically with other household level data they likely have.
https://www.mdpi.com/1424-8220/24/7/2111