Ferrum: Stud Finder & Metal

Ferrum is an honest, calibrated measuring instrument built on your iPhone's magnetometer. It starts measuring the second you open it — continuously, with no timers, no upgrade prompts, and no subscription. WHY FERRUM EXISTS Wall scanners on the App Store interrupt your measurement to sell you something, charge weekly for a sensor your phone already has, or dress up the Earth's own magnetic field as a "detection". Ferrum does none of that. You pay once. There are no ads, no accounts, and the app never connects to the internet. CALIBRATED, NOT GUESSING The Earth's magnetic field runs 25-65 µT, and your phone adds a bias of its own. Ferrum measures that background first, then shows you only the change — the number that actually means something. Recalibrate any time with one tap. FOUR MODES, ONE ENGINE - Stud - find the screws that hold a wooden stud in place, with a narrow threshold tuned…