Found my property line iron pin

Just when I thought I had seen pretty much everything the iPhone could do, I found this app. My guess is that it is using some function related to the compass and magnetic sensitivity. Its definitely not the camera and is only sensitive to ferrous metal as stated). I have a 6+, and this app worked perfectly. I calibrated it on a known iron pin (set sensitivity at 30) then went hunting in about a 9 sq. ft. section of grass for the next pin. The app worked perfectly with a beep when I swept over the hidden pin (sweeping fairly quickly about an inch above the grass). Awesome!

DSeabury about Metal Detector and Spy Camera