The presence of an intrusive activity monitoring device like CCTV in the area can make people feel uncomfortable when they know they are being monitored and recorded. With Wi-Fi, it sits transparently in the environment. By its nature, Wi-Fi cannot capture an image and thus making people feel a lot more comfortable to be in the area.
The recent study shows that Channel State Information (CSI) from Wireless Ad-hoc System for Positioning (WASP) operated on 5.8GHz frequency can be used in activity recognition.[1] This research tries to apply the same principle with Wi-Fi to measure both activity and location of a person.