Metal Detector EMF Meter is a free iPhone app developed by Steve Yoes that allows you to convert your iPhone into an EMF meter.  Using the device's built-in compass, the Metal Detector / EMF Meter app displays magnetic field readings in raw form. This program was made to help people like scientists, educators, students, engineers, and even ghost hunters detect magnetic fields.

The strength of magnetic force fields can be detected in all three axes (x, y, and z) and measured in microteslas (T) with this app. In addition, the "Readings Log" function allows you to keep track of your readings alongside the time and date of each occurrence. To take a reading for an experiment, you can halt magnetic readings by pressing the clock button.