Wireless Routers as Motion Detectors

Comcast has added motion detection as a feature to its wireless routers: The feature sends push notifications to users when motion is detected near a connected device, such as a TV or printer. It has different settings for when people are home, asleep, or away. The Xfinity app also lets users see live motion activity and a feed of recent activity. Comcast acknowledges that the system has some limitations. Home size, layout, building materials, and the placement of the router and connected device

Source: Schneier on Security