hall-effect-sensor metaldetector

[bernte_one]

I read something about Hall-Effect sensors in wiki.

http://de.wikipedia.org/wiki/Hall-Sensor

there is written
If current and magnetic field strength is known, the Hall sensor can be used as a metal detector.

here a source for a detector

http://books.google.de/books?id=RM2lEleKFAwC&pg=PA20&lpg=PA20&dq=hallsensor+metaldetector&source=bl&ots=O-3EcoTOP9&sig=D2KotRK9wqtIXI3V95u4sOO53EI&hl=de&ei=qh2DTcqTLoPEsgbUzIyCAw&sa=X&oi=book_result&ct=result&resnum=5&ved=0CFQQ6AEwBA#v=onepage&q&f=false

could this be interesting for us maybe for deepscanning large iron objekt which change the natural magnetic field ??? or only for pinpoint use?