Product review (4 stars): "Trend" arrows don't work.  Otherwise, good.
It synchronized automatically once batteries were in, and has a very readable display.  Seemed to work well except the "trend" arrows didn't work for about 1/2 hour.  The outdoor temp. had fallen 15 degrees and the humidity had risen 10% since I put the sensor outdoors (about 1/2 hour ago), but the trend arrows still showed "steady" for both.  But after about an hour, they were working.  They just don't show short term trends.