Product review (5 stars): Excellent
This works fantastically. It is tiny, so fits perfectly in even a small case. It is super responsive - I have it in my sons room and anytime I open the app anywhere in the house I get an instant humidity and temperature reading.  The app is really easy to navigate, and you get a nice list of all the sensors you own along with the name of whatever instrument (or other humidity/temperature sensitive thing) you are monitoring.