Comcast has rolled out a new motion sensing technology to its latest home routers, allowing homeowners to receive notifications about activity detected inside their house while they are away.

The free feature, called Wi-Fi Motion, turns newer Xfinity gateways into motion sensors by detecting interruptions to the Wi-Fi signal of the wireless network, and sends a notification through the Xfinity app.

As first reported by The Verge, the new Wi-Fi Motion feature works for advanced Xfinity gateways XB7 and newer models and is opt-in, which means users can choose whether to switch on the feature in the Xfinity app. As quoted by the publication, customers can use this feature for “motion detection in their home and for a basic level of security.”

There is a privacy trade-off. By enabling the feature, Comcast says it may disclose information generated from a customer’s use of Wi-Fi Motion to outside parties under a broad array of reasons — and Comcast also says it doesn’t have to tell you.

“Comcast may disclose information generated by your Wi-Fi 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,” reads an Xfinity support page.

That’s something to consider before you switch on the feature, particularly if you’re privacy conscious.