Product review (3 stars): Worth the money!! But Beware!
I purchased this item for use with my gun safe, one unit in the safe and one outside so I can monitor the temperature and humidity difference. These monitors are fairly accurate, there's a .2 difference in temp. and a 9% difference in humidity between the two units. This is a good buy at 10 bucks.
UPDATE: Have had an opportunity to do some additional testing on these units and while the monitored difference temp. remains within .5 deg. the humidity indication is not only incorrect but there are at times as much as a 30% difference between the two units, having said that, these units are still, but to a lesser degree satisfying my needs and so have only lowered my rating by one star.