Product review (4 stars): Smiley guy absent
Bought 2 with my new whole house humidifier to check humidity on two other floors.  Works great, batteries seem to last long.  Only thing that is weird is that the smiley faces don't seem to work.  I was going to use the smiley faces to figure out if I was setting rooms at the right humidity.  It never shows 90% of the time so I don't use it at all.  Nice that there is a magnetic back to stick to things.