This is really a nice and colorful gadget. Taking measures is very simple, and at a first impression it seems reliable. However, it is not, or at least not always, for reasons that I could not precisely determine. Sometimes when my baby had 38.5 (according to a standard thermometer with rectal measurement, repeated), it gave a falsely reassuring 36.3 (even with repeated measures in the correct "behind the ear" point. Even on myself, when repeating measures, for how much care I put in applying it to the same point, I occasionally have some readings which are very far from the others (even by 1 - 1.5 degrees C). My personal theories about this behaviour are:
a) either it is normal that sometimes there are big differences between rectal and "behind the ear" temperatures,
b) and/or taking the "behind the ear" temperature is too sensitive to occasional cooling of the skin due to unpredictable reasons, endogenous as well as exogenous.
In conclusion: a very nice tool, beautiful and a pleasure to use, but knowing that it is accurate only in some 80% of cases. I am not sure if I would use it to measure the temperature of my baby (or of myself) in critical situations, e.g. when it is close to 39C, to decide whether to take anti-fever medicaments or not.