Product review (4 stars): It works nearly perfectly
This small device actually works well.  An air conditioner installer using his thousand-dollar device measured my room temperature and found it only one degree off of the temperature shown on this low-cost digital thermometer.  Close enough for me.  The humidity numbers correspond well with my experience of what various indoor humidity levels feel like but I cannot attest to the level of precision.  So far I have used only those two functions.  It certainly seems worth the relatively low cost.