Search for Buried Treasure With This DIY Magnetometer - IEEE Spectrum
Metal Detectors and Magnetometers
Overhauser magnetometer-gradiometer MaxiMag
Magnetometer Metal Detector - Apps on Google Play
Amazon.com: UFO Detector - Internal magnetometer interfaced with microcontroller for 24 hour/7 days a week monitoring for magnetic anomalies that have been reported with many UFO sightings : Electronics