Are you talking about "Motion Sense"?
"Motion Sense" is a feature that only Pixel 4 and Pixel 4 XL have as it relies on a special hardware that only these two phone models feature.
"Motion Sense" can only be used in specific white-listed countries and can only be used to:
- Silence interruptions
- Skip songs
- Play or pause music
None of these features are present on AOSP and they have nothing to do with privacy and security, thus they are not part of GrapheneOS.
Even on Stock Android third-party applications cannot use "Motion Sense" functionality.
For more information please refer to the link above.
Hope this helps