Just "Measure" on the iPhone. For instance, just measured the back wall of a closet. Then went to the next room and could see where the back wall of the closet was in AR.
Samsung, at least ultra line, has Lidar too and exactly same type of measure app (on top of some AR doodling). Just tried it and its actually pretty precise (on S22 ultra). I wouldn't build a shelf based on just that data but otherwise nice little addition to the toolset.