Product review (2 stars): Poor initial calibration and unmatched readings
The out-of-the-box accuracy of this unit was very poor. When placed side by side on an indoor table, with a calibrated temperature probe in between, the units consistently showed a 2 degree F difference, with one or the other sometimes matching the high-accuracy device. The humidity measurements were even more off, by 12-20 percentage points at all times. I did not expect laboratory-grade calibration, but from a company with "accuracy" in the name and the many rave reviews of performance, I did expect at least an initial matching calibration - dead on with the easy temperature measurement, perhaps 5 percent variance with the trickier humidity.

I even opened the units up to see if there was any kind of field or assembly-line calibration I could adjust, but it looks as if these are calibrated at the time of assembly and not adjustable short of some elaborate bench work.

I had intended to use this pair in a giant terrarium, to monitor temp/humidity at opposite corners, but the lack of even matching performance and questionable overall accuracy makes the unit useless for such purpose. I guess if people simply put one unit on the wall and one outside on a tree, they'll never notice that there's considerable calibration difference between the units, and instead rave about how well it works. If approximate temp and humidity are all you want and an app for your smartphone is too inconvenient, I guess this unit will work for you.