Product review (3 stars): Handy Cheap spot checker.
These little meters are very handy. Cheap enough to buy lots and scatter around the warehouse to track conditions.
I lined them all up on a table and the humidity and temperature readings all agreed with each other plus or minus a few percent on the humidity (typical for humidity devices) and right on for the temperature. The only problem is the temperatures are 2 degrees lower than a calibrated thermometer, and no way to adjust, or switch to Fahrenheit. That was why I dropped the rating to 3 stars.
Still, at the price you can't beat them for monitoring for changing conditions.