PCWorld reports that Comcast has launched WiFi Motion, a feature that turns existing Xfinity routers into motion sensors using standard Wi-Fi signal interference. The technology is integrated into the Xfinity Shield security option and is available free to customers through the Xfinity app, with no cameras or video recording involved. While convenient, data privacy concerns remain regarding how movement information may be shared with third parties. Comcast, the largest residential internet service provider in the US, is introducing a new feature called "WiFi Motion" that enables physical motion detection using nothing but Wi-Fi signals. By monitoring signal interference, WiFi Motion can accurately detect and track people and objects in and through physical space.