There really is an app for everything.
You can turn your smart-phone into a stud finder, courtesy of its magnetometer sensor, and some clever programmers. I never realized that a stud finder doesn't find studs, it finds the nails which are driven into the studs. Nails are metal, which the magnetometer can sense.
One more magic bubble burst.
There are a number of different apps available, with the links below just a starting point.
Android > https://play.google.com/store/apps/details?id=com.goldsequence.magneticstudfinder
iOS > https://itunes.apple.com/us/app/stud-find/id328575868