I use a Wagner pin-less, use it a lot both out in the drying piles to monitor my stacks, and also down in the woodshop checking how dry stuff is before taking it down to final dimensions. The good ones are pricey, but I use mine often, and it's one of those things that if I'm going to have one, I want a good one. If you're just looking to monitor roughly how dry your stickered pile is getting, I guess you could get away with one of the cheaper ones that just measure resistance, and thus moisture.