Unless you put your iPhone in a place where body heat can't warm it an an electronic thermometer is pretty useless. Most mountaineering watches (Suunto & Co) sh

Unless you put your iPhone in a place where body heat can't warm it an an electronic thermometer is pretty useless. Most mountaineering watches (Suunto & Co) show the correct temp. only after 20 mins. or so. And that's without taking into account the heat the device itself produces, which may be non-negligible for the iPhone.