Comcast is turning compatible Xfinity Gateways into motion sensors with a new feature called WiFi Motion, which uses changes in the Wi-Fi signals around your home to detect movement.

The feature is part of the cable giant’s new Xfinity Shield offering, which is available to Xfinity Internet customers at no extra cost.

It started rolling out through the Xfinity app last week, although you’ll need a compatible Xfinity Gateway; with the XB7 and newer models supported.

The idea behind WiFi Motion is that it doesn’t require a security camera or a dedicated motion sensor.

Instead, the Xfinity Gateway monitors changes in the radio-frequency signals between the router itself and any Wi-Fi-connected devices around the home. When you move through the rooms, your body interferes with the signals.

Comcast's software can detect those changes and, if you've opted into the feature, send an alert to your phone through the Xfinity app.

So, rather than buying a motion sensor and sticking it to a wall, your existing Wi-Fi equipment can do the job.

WiFi Motion doesn’t record video, capture images or attempt to identify who is moving around; it's simply detecting movement.

So it’s not really a replacement for a proper security system; Comcast is pitching it as an additional layer of awareness.

You can set up different modes depending on what you're doing, with Home Watch for when you're around, Away Watch for when you're out and Dark Watch for overnight.

Because it's using Wi-Fi rather than a conventional PIR motion sensor, there's no need to worry about batteries running out or finding somewhere to physically mount another sensor.

Comcast is effectively taking something that's already sitting in millions of homes and giving it another job.

It’s not a completely new idea, though. Wi-Fi sensing has been knocking around the smart home for a few years now.

WiZ, for example, introduced its SpaceSense technology in 2022, allowing its Wi-Fi-connected lights to detect movement without dedicated motion sensors.

It works by measuring changes in the Wi-Fi signals between multiple WiZ lights, and can then use that information to switch lights on and off automatically.

Comcast states the average Xfinity customer has 36 devices connected to their Wi-Fi, giving the Gateway plenty of data from which to work.

It’s an opt-in service and requires an Xfinity WiFi Gateway. Compatible gateways include Technicolor TXB7, XB8, XB9, XB10, MXB1, and XER10.