For passive humidification I've tried PG solution and credos, gel (like the humicare stuff that CI sells or what Xikar calls "beads" - a gross misnomer), heartfelt beads, boveda packs, even the silica kitty litter and just for grins, a red clay brick that had been soaked in water. The ones that have worked the best, with the least hassle in tightly sealed non-permeable containers (like your wine cooler) at least for me, are the Shilala/HCM beads.
As for hygrometers, I've been quite pleased with the HygroSet (rectangle) adjustable hygrometers.
and YMMV. Different humidors behave differently and may need different humidification sources; for example, the brick worked great in a leaky wood humidor.
Both are available from
http://www.hcmbeads.com/