I recently built an WLAN Thermometer which needed to be partly whaterproof and support temperatures under 0 and over 85 degrees celsius. Therefore the usual temperature measurement chips like DHT11 or LM35 couldn’t be used, especially as the surrounding circuits might be damaged by the steam of the sauna environment. After a while I found the DS18B20, which has an metalic and whaterproof end and perfectly matches the requirements. In china the one-wire-supporting chip currently costs around 2 USD and comes with a 1m whaterproof cable.
The ESP8266 works with 3,3 Volts which isn’t very common among my old power adapters which is why I soldered a chinese version of the AMS1117 (an Lm2596 step down controller) on the board, which enables the setup also to be run by USB cable as you can see on the pictures.
That was my useful christmas holiday project 🙂