Comcast is activating free Wi-Fi motion-sensing technology on millions of existing Xfinity routers, turning them into makeshift activity monitors without customers needing to buy extra hardware. The feature, called WiFi Motion, is being rolled out today as part of a new Xfinity Shield service and works by detecting disruptions in the Wi-Fi signal between a home's gateway and connected devices, then sending alerts through the Xfinity app, similar to a standalone motion sensor.

WiFi Motion requires an advanced gateway (XB7 or newer), is opt-in, and can be toggled on or off in the app, alongside new modes called Home Watch, Away Watch and Dark Watch for different situations. Xfinity Shield is free for all customers and also bundles improved malware and phishing protection plus enhanced parental controls, while a pricier Xfinity Shield Select tier adds an upgraded indoor camera with AI-powered alerts for people, pets, vehicles and packages. Comcast says it has spent three years refining the underlying algorithms and views the feature as offering "adequate" basic security for the average household rather than replacing dedicated camera and sensor systems.