This app was mentioned in 4 comments, with an average of 1.75 upvotes
Yeah, there's an app called weatherstation which displays the sensor readings from the phone. It is fairly accurate, I compared it to two other thermometers and the readings were the same. If the phone has been in your pocket for a while you need to let it cool down and acclimatise before taking any measurements. /u/fluteitup I don't use my phones with a case.
If you wanted to buy a phone, the Galaxy S4 is actually a pretty decent idea. Has a bunch of good sensors etc. Temperature, barometer, humidity, and even geomagnetic if you needed it. Could be interesting if you could interface this to say send a text if it reached over X degrees, keep a track on relative/absolute humidity, etc.
Great app for sensor data: Weather Station
This is a bit tangential to your original question but I'll mention it anyways. The Galaxy S4 would be great for something like this because it has a mostly complete suite of sensors. Temperature, barometer, humidity, and even geomagnetic if you needed it. Could be interesting if you could interface this to say send a text if it reached over X degrees, keep a track on relative/absolute humidity, etc.
Great app for sensor data: Weather Station
https://play.google.com/store/apps/details?id=com.aminor.weatherstation
This was what is I had used at the time.