Electromagnetic Field Detector #1:

Electromagnetic Field Detector #2: This circuit is sensitive to low frequency electromagnetic radiation and will detect for example hidden wiring or the field that encompasses a transformer. Pickup is by a radial type inductor, used as a probe which responds well to low frequency changing magnetic and electric fields. Ordinary headphones are used to for detection. The field that surrounds a transformer is heard as a50 or 60Hz buzz.  

Magnetic Gun: When optimally tuned, it will propel a small slug about 1.5 meters high, or 2.5 metres horizontally 

Magnetometer:

Method offers Fail Safe Variable Reluctance Sensors: 11/27/01 EDN-Design Ideas  / PDF contains multiple circuits - scroll to find this circuit

MilliGauss Meter:

RC Netw1ork Eliminates Precision Reference: 08/04/94 EDN-Design Ideas 

tw1o Diodes Change Demagnetizationsignal Polarity: 04/12/01 EDN-Design Ideas /  PDF contains multiple circuits - scroll to find this circuit.