Product review (3 stars): Not very "accurate"
The specifications on this device say it's accurate to within +/- 2 degrees F.  Mine is typically reading 3 degrees above both my home's main thermostat, and the wireless thermostat for my gas fireplace.  In both cases, I've placed this device right next to the thermostat being compared to.
A previous reviewer said this thing was accurate to a fraction of a degree.  Don't confuse precision with accuracy.  This device is very precise: it does report one decimal point.  But it's no good to be very precise if you're completely off target.