Product review (2 stars): Inaccurate, cheaply made monitors.
One of the units ordered was totally out of calibration.  Temperature was off by ~10 degrees.  Humidity was also off by about 10%.  The second unit isn't too accurate either, but not as bad as the first.  $20 sure don't get you much these days.

I'll stick to my temperature/humidity measuring units from the 80s.