Last month Google updated the Nest Hub and Nest Hub Max so that they could use ultrasonic sensing to tell when a person is nearby. While the Hub Max includes a camera that it could already use to surface Proactive Notifications when people are around, the original Hub doesn’t have one at all. By sending out a high frequency chirp and listening to the echoes on embedded microphones, the smart displays can detect a person-sized object in the room without pulling in a video feed.

In a new blog post, a team member explained more about how the technology works, and that it changes the available information based on distance. When someone’s further away, it features larger text, as they move closer it can shift to include more details and touch controls. So far the technology has been used for timers, commute times and weather, but over the next week an update will add “reminders, appointments and alerts.”