Product review (5 stars): Just as good as anything out there
Bought one of these last week and use an Oasis hygrometer in my Martin D-16 case , the readings from the planet waves humidity and temperature sensor are always within 1 to 2 percent variations in the temperature , and the humidity changes compared to the Oasis hygrometer is always within 1 to 3 percent compared to this device. My verdict , for the price this is as good as any hygrometer/humidity , temperature sensors on the market , it has a hooked velcro back so it should lay sturdy  in any case , I even put some velcro strips on the TV stand in my living room so If I need to I can attach it there and get an idea of the humidity in the room. I have electric heat in a fairly cold climate so I keep my acoustics in their cases as much as possible , Planet waves makes some great stuff and this little device is no exception