EMF Detector is an app that uses the magnetic field sensor on your phone to take electromagnetic field readings.It will display EMF in micro Tesla (uT).

You can use this app to study magnetism and electromagnetism or use it as a metal detector.

An EMF meter is a scientific instrument for measuring electromagnetic fields (abbreviated as EMF). Most meters measure the electromagnetic radiation flux density (DC fields) or the change in an electromagnetic field over time (AC fields) essentially the same as a radio antenna but with quite different detection characteristics.
The two largest categories are single axis and tri-axis this app will works as a tri-axis EMF meter.