UPDATE: If you have an iPhone 3G or better or an Android phone, YOU HAVE A FREE EMF METER. See this post.
If you’re looking for an EMF detector on the cheap, look to your local hardware store or home improvement department at your local bog box store.
You’re looking for a “non-contact voltage detector”. The one I found at my local Walmart was around $10 and looks kind of like a bright yellow blocky pen. These things are typically used to see if an AC circuit is “live”. They happen to work on the same principle as EMF meters and can be used to locate areas of very high AC EMF activity caused by non-paranormal devices like wiring, TVs, and computer monitors. They are great tools to rule out normal sources of EM radiation.
There is, of course, a down side. First, they are detectors, not meters. The audio signal and flashy light won’t give you an accurate measurement of the field. Second, they are not the most sensitive devices in the world, but they’ll do for locating the source of explainable AC EM radiation. If these things detect voltage where you spend a lot of time, you might consider moving away from the source of the radiation…
But for the price, and small size, these might be a good addition to your investigation kit.