I've only ever compared the security wand I bought used, to a cheap old stud finder.
The wand was a tiny bit better.
Great tool and I think seemingly a lot handier to have than using a magnet alone.(if doing a lot of salvaging)
Not used a rare earth magnet before, but I'd not discount it for a belt and braces approach,
as I've encountered a buried end of tack once or twice, which doesn't do a bandsaw blade any good at all.
Could try and get some of them sometime, seems a bit risky getting ones from overseas, should it stick to the side of some container along the way.
Worth the twenty quid or so for what a bandsaw blade costs.
I do question mine occasionally when digging out a big hole and its getting bigger and bigger,might miss something very occasionally with something minuscule, i.e pin head sized, but it never lies.
I normally go over the timber again before working with it, once its stored for a bit.
This one, as with all of them I guess?, don't seem to eat batteries when left unused.
(is that a thing with only cheap calipers?)