A free program for Android, by Droidrec.

When using this app, you should be aware that not all metals are equally magnetic. For example, the iron content in the blood is much higher than the steel content. So, the app may not work as expected. However, in general, this tool is accurate and works well for most people. It is not recommended to use this app for medical purposes. In this app, you will see the magnetic field level (EMF) in μT (micro-tesla), which is equal to ten times of mG (milligauss).

This application uses your device’s built-in sensor magnetometer to detect the electromagnetic field generated by a magnetic metal.