>xfinity now offering motion detection via wifi
https://www.xfinity.com/support/articles/wifi-motion
What else could wifi be theoretically used for?

This is basically disclosure that they have been monitoring us for who knows how long with RF.
>researches use wifi to see through walls
https://www.youtube.com/watch?v=fGZzNZnYIHo
From what I believe the human body is electrical and has a biofield, I think they can use RF to detect emotional state. They may be even to somehow read your inner monologue, not quite sure.