As people move through a space with a wi-fi signal, their bodies affect it, absorbing some waves and reflecting others in various directions. By analyzing the exact ways that a wi-fi signal is altered when a human moves through it, researchers can “see” what someone writes with their finger in the air, identify a particular person by the way that they walk, and even read a person’s lips with startling accuracy—in some cases even if a router isn’t in the same room as the person performing the actions.
from Stowe Boyd http://www.stoweboyd.com/post/149506636317
