When the router becomes a motion sensor, who holds the log?

On 18 August 2026, Comcast made Wi-Fi motion sensing available on millions of the Xfinity gateways already in American homes. No new hardware, no camera, no extra charge. TechCrunch reported the launch the same day.

For anyone who works with Wi-Fi sensing, that is a milestone. A technique that was a research topic a few years ago now ships as a standard broadband feature. The coverage that followed was about something else.

The sensing was not the controversy

Comcast's feature is opt-in and switched off by default. It creates no video and no images, and Comcast says it does not monitor the motion or the notifications itself. Xfinity's own description says motion activity is retained for up to seven days.

The criticism landed on one sentence in the terms. As The Register quoted it, Comcast "may disclose information generated by your WiFi Motion to third parties without further notice to you in connection with any law enforcement investigation or proceeding, any dispute to which Comcast is a party, or pursuant to a court order or subpoena." The Register noted that the terms do not say which information, or which third parties beyond law enforcement.

That is ordinary legal language for a service provider. It drew attention because of what the data is: a record of when people are moving inside a home.

A motion log is personal even without a picture

"No camera" answers one question. It does not answer what a history of movement reveals: when a home is empty, when someone gets up at night, when a routine changes.

We make the camera-free argument ourselves, so we should be exact about its limits. A system that never forms an image has no image to leak. It can still produce events, and events kept over time are a log. Whoever stores that log can be asked for it.

Four questions for any sensing provider

These apply to us as much as to anyone else:

• Where is the signal interpreted? In the home, or on someone else's servers?
• What leaves the building? The raw signal, or only an interpreted event such as "movement in the hallway"?
• Who stores the history, where, and for how long? A week in an operator's cloud and a year on a local device are different exposures.
• Who can be compelled to hand it over? The answer follows from who holds it and in which jurisdiction.

How Stillsense answers them

Stillsense interprets the Wi-Fi signal on a device in the building. The raw signal does not leave the premises; only interpreted events and alerts are sent to the endpoints a customer has defined.

There are two ways to run it. Self-hosted, all data stays on the customer's premises. With Stillsense Cloud, interpreted events are stored on a managed service hosted in Norway, with defined retention and deletion routines.

Neither option makes an event history disappear. On Stillsense Cloud we hold interpreted events and are subject to Norwegian law. Self-hosted, the customer holds them. What the design does is keep the most detailed data in the building and make the remaining log small, located and owned by someone you can name. Our security page sets this out.

What this means for operators

If you run a network, the Comcast launch shows that sensing can ride on hardware you have already deployed. It also shows what customers and journalists will read first: the terms.

An operator that adds sensing has to decide whether it wants to hold a movement history for every subscribing home. Interpreting on the gateway and keeping the history with the customer is a product decision as much as a privacy one. It limits what the operator can be asked to hand over, and it gives the support team a short answer when a customer asks who can see the data.

Stillsense Core is the sensing engine we license for that purpose. Talk to partnerships about what stays on the device in your hardware.

Details of Comcast's service come from Xfinity's published description and from reporting by TechCrunch and The Register in August 2026. We have no knowledge of how the service is built beyond those sources.