By now, you’ve heard: the new Pixel 4 has a tiny radar chip inside it, which allows you to swipe or wave your hand to do a few things. More importantly, Sense (as Google has branded it) is designed to detect your presence. It knows if you’re there.

from https://www.theverge.com/2019/10/15/20908083/google-pixel-4-project--radar-motion-sense-explainer
https://cdn.vox-cdn.com/uploads/chorus_asset/file/19287838/Google_Soli_0253.jpg