Product review (4 stars): Helpful
Helps us understand why we're uncomfortable sometimes. For example, right now the relative humidity in my office is 15%, well into the "too dry" range, and my throat and lips attest to that.

There's some sample variance in calibration. I've put two of them next to each other and they disagree by a degree of temperature and a percentage of humidity. Not a big enough difference to make them not useful.

The battery lasts for months.