Tried the "LiDAR Measuring" app again after realizing it is point-on-a-surface to point-in-space. It uses light and has to reflect off something.
First tried it to find height of desk and cat scratch post inside. It was withing shaky hands range of exactly what steel tape said or about .10 inches.
Ran a tape down the hall on floor and fixed on chest high point on wall and got "High Accuracy" readings out 25'. They matched tape as nearly as you can eyeball from phone at chest level to tape on floor.
Ran it up the street from a telephone pole. Still said "High Accuracy" at 150'. You can move much faster than with Measure which seems to be point-in-space to point-in-space.
Then, ran a steel tape out from garage door with a 10 lb steel block holding tape down. Fixed point chest high and walked backward. Got eyeball chest to ground accuracy at 70'. Put phone in pocket for a few seconds and readings were a couple of feet off when I took it back out.
With some careful set up, marked a 30" board within about a kerf width of what the tape said.
Used correctly, you could "gain confidence" you had the right point on raceday. But neither Measure or LiDAR Measuring will replace a steel tape anytime soon.