I will definitely keep this app on my iPhone.

Yes, this APP does work!
It only detects small metal, it didnt detect my steel shovel but went crazy when it got close to the steel toe on my work boots. It also worked to find a drywall screws in a wall to help me find the stud, but barely detected my steel desk.
All I can say is that its a hell of a lot better than nothing and free!
I will definitely keep this app on my phone.

JBLopes about Metal Detector and Spy Camera, v1.1