Fez based metal detector

I would like to build a metal detector for my son. I am thinking about using Fez mini. I wonder if anybody here have experience with metal detectors and can share any information. I am at the research stage right now so any information is welcome.

It can be a good candidate for contest:

Are you going to build the detector from scratch or use this one

I would like to build discriminating detector - different types of metal, depth, size.

Personnally I am not familiar with this type of metal detector.
But I found this forum that have a lot of info. on the mentioned detector:


Thank you. I will take a look.