eTesla app for iPhone and iPad

By using data from the phone internal compass,
This app can measure the magnetic field generated from metals
Or high electromagnetic emission from High Voltage line ,Transformer ,
Electric motors,and some home appliance such as microwave oven.

The units of measure is Tesla -µT : Nikola Tesla (10-Jul-1856 - 07-Jan-1943)
inventor of the Tesla coil and developer of inductor motor working by alternate current.
The normal earth emissions is around 20-40 µT.

High magnetic field can reach 200 µT (e.g. near to speakers).
In very high magnetic field (e.g. near electric motors ) it can be over 300 µT
such high magnetic field ,can easy damage credit ,mechanical watch .

If the phone has been exposed to e high magnetic field , the sensor need to be recalibrate by just shake the phone until the data reader become normal range.

A alarm can be set by the slider, over that value the value become red and the phone will vibrate.

So: stay away from strong magnetic field : find it and avoid it.