I was messing around with my Arduino board and figured out how to make a cheap portable electromagnetic field (EMF) detector. It only requires a led, 3300000 Ohm resistor, and wire. As I approach an EMF the led gets brighter, so I can locate the source. Messing around with the code and resistor values I can change the sensitivity of the device; when I first made the EMF detector I could only find one place to stand in my apt where it didnt go off. I am working on getting a commercial EMF detector that spits out quantitative values so I can calibrate my version and have it do the same on a LCD. *UPDATE you can decrease the sensitivity of the device by making a loop with the antenna. Also the code can be found on my website, aaronalai.com