XrayAR
Hidden studs and pipes — the wall is opaque to optics, not to magnetism.
What it does
Glide the phone over the wall. An arc draws underneath where the magnetometer reads a strong signal — the ferromagnetic centre of a stud, the steel jacket of a cable run, the rebar in a slab. The arc is anchored to the wall, not the screen, so a second pass over the same spot shows the same line where the first pass left it.
How it works
The magnetometer samples ~30Hz. Each sample is a vector; its magnitude jumps when the phone passes over metal. A simple debouncer + threshold turns the magnitude trace into a series of detected hits. Each hit is projected onto the wall plane (using ARKit's depth + plane detection) and drawn as a 1cm radius arc. Successive arcs connect into a path so the visitor sees the centerline of a stud as a continuous line, not a dotted scatter.
What it's built on
CoreMotion's CMMagnetometerData feed. ARKit plane detection for the wall surface. A custom debouncer for the magnetometer-to-hit conversion. The arc is rendered via a single RealityKit entity that accumulates its path as you sweep.