The built-in compass uses the earth's magnetic field to calculate the deviation from magnetic north. As with every compass, if you put a piece of metal nearby, it gets deviated. That's what i use here to detect metal.

Testing: Place your device flat on a surface. After starting the app, the gauge should show zero. If it doesn't, take your device and write a couple of "eights" in the air (this is to get rid of magnetism which might get stuck in the sensors).>
Then use a pair of scissor or something the like and move it slowly to the right side of your device. At a distance of approx. 5 cm. the gauge should start to move. Take your device and move it with its right side near metals, and see if the gauge shows values.

Current status of this app

This is far from finished, but as we both are quite busy at the moment, we'd like to share the current beta of this app.

All gauges are fully functional. Clicking sound and vibration working too. You may turn them on/off using the corresponding buttons on the left.
To exit the app, use the lower right button.

The camera button has a new meaning as of v0.2.0.0:

It enables a test mode, where sensor readings are simulated. Use the sliders to advance the main/aux gauges

todo's we're aware of:

- artwork needs final polishing
- sliders do slide but have no effect whatsoever, temporarily used for debugging
- screenshot (camera) button switches debugging mode (this will change in a final release)
- detection algorithm still crappy
- sound and vibration status not saved on exit