I've been doing a little more readin on this Natural EMF Meter, and it claims to be able to detect weak DC fields, while ignoring AC.
I've played with one myself, and have seen it work. Insomuch as when a person walks about in a room, the needle will go off, seemingly detecting a person's movements. Whether it's actually detecting my movement itself, or the bioelectric field I'm putting off I suppose is up for debate. But the other settings on the meter do seem to do as advertised.
Would it be safe to say then, that AC is almost always artificial, while weak DC is mostly natural?