Product review (4 stars): Don't Expect A Miracle
I got these little babies knowing that they would not be super accurate with their hygrometers, and I got exactly what I expected.
Pros: They are super cheap in this bundle. They also have a nice, small footprint. The temperature readings are pretty close. Well within the range they specify.
Cons: Hygrometer is more of a ballpark figure. They will give you an idea of what your humidity readings are. My home has forced air heat with no humidifier attached, so we get super dry. These will say we are anywhere between 10% and 25%, even when all four are right next to each other. It seems that they lose accuracy the dryer it gets. When I have them in the bedroom with the standalone humidifier, they get more in sync with each other. Once humidity gets over 25-30%, they are pretty much in line with each other (+- 5%).
Final Report: I give their ability 3 stars. I give their price 5 stars.