If only privacy from tech needed to become a bigger joke, Amazon’s vision of smart home is now inching closer to reality. Starting this week, newer Echo and Echo dot speaker will start detecting people within your room, thanks to the ultrasound tech that Amazon first mentioned at its fall hardware event in September this year.

The Echo and Echo dot fourth-generation speakers will now have the ability to use ultrasound in order to detect the presence of people in a room, and switch on or off connected devices.

This feature is not an unexpected one, given that Amazon had announced it at its fall hardware event this September. The feature has been rolled out for fourth-generation Echo Dot and Echo speakers. You can disable or enable this feature using the Alexa app (under Motion Detection in the app settings for the compatible Echo devices) and set up occupancy routines to utilize the feature in many ways, such as turning on lights while entering a room and turning them when the room is empty, or play music when motion is detected near an Echo device and turning it off when the room is empty.

Amazon said that the speakers will emit an “inaudible ultrasound wave” to detect presence. This ultrasound will travel in all directions and bounce back to the microphones on the device. If there is a motion near the device like people are entering a room, the time in which the emitted sound frequency returns back to the device is altered, thus making the device aware of occupancy.

If you think this sounds similar to the motion-sensing feature on the Echo Show devices, you are not the only one. It is similar, but the Echo and Echo Dot speakers rely on ultrasound while the Echo Show uses cameras to detect presence and motion.