Can a smartphone measure temperature like a thermometer?

Why smartphones don't have thermometers?
Of course, smartphones are infinitely more complex and capable than a basic digital thermometer. The issue here is not that manufacturers can’t fit yet another sensor. In fact, smartphones have multiple thermosensors already. They’re used to measure the temperatures of the battery and the chips, preventing disaster in case something goes wrong.
But these same parts are generally used to dump heat from the internal components, or in other words, as a basic passive radiator. Essentially, manufacturers would have to put a thermometer on a radiator and still provide measurements that make sense for the user.
Smartphones with thermometers do exist
The idea is nothing new and manufacturers in their constant pursuit of innovation did give it a try. Namely, Samsung and Motorola had phones with thermometers. Samsung did it with the Galaxy S4 and Note 3. According to the instructions for using this feature, measuring the temperature required you to leave the device to cool off from any heat it might have accumulated during use and leave it somewhere so it doesn’t get warm from your hands.
As you might imagine, it’s far from practical and even after following the instructions, the accuracy of the measurements was doubtful. That’s probably why Samsung promptly dropped the idea and never tried it again.
Don’t trust thermometer apps
So, while our phones can do a lot, as long as they’re a thermal roller coaster, we won’t be getting any useful ambient temperature readings from them.