Product review (5 stars): Really Nifty Temp/Humidity Device
These came to me as a 2 pack of Temp/Humidity gauges with digital readouts.  I am really pleased with this item and will keep one in each end of my home.  I line in the Pacific Northwest and our location is high desert with a really dry climate most of the year.  I also have some wood musical instruments that really do need to be kept humidified to prevent the wood from cracking.  I try to keep enough humidity in the house via a Honeywell 9 gallon/day humidifier and with these instruments I have a constant read on the moisture levels in my home.  Additionally, you will breathe easier with the proper humidity as well as save on heating.  You feel warmer with more humidity in the air.

You will have to supply two AAA batteries for each of these units, battery life is estimated to be two years.