Product review (4 stars): Cheap and cheerful.
Does a lot of stuff for small money but I don't think it is very accurate.  I'm just referring to the temperature reading on the main unit.  Probably close enough, and I may be introducing an error by mounting on exterior wall, but it seems to be displaying a couple degrees below room air temperature.  There is an offset adjustment that might take care of this.  I'll have to experiment.  Only other point worth noting is that while the main unit temp can be displayed in degrees F I find no way to change the remote transmitting unit.  It would be nice if both displays were using the same scale.  Given the price I am a happy camper but would rather pay double for much higher precision if that was an option.