Temperature and humidity measurements are a nice addition ... He decided to take an in-depth look at the DHT11 sensor; which you can get your hands on for under $3 if you know where to look.

The Anavi Thermometer Development board is fully compatible with the Arduino ... powered by an ESP8266 processor. It comes with a built-in DHT22/AM2302 temperature and humidity sensor and has ...

A lot of people have used ESP8266 to add inexpensive WiFi connectivity to their projects, but [Oscar] decided to take it one step further and program an Arduino over WiFi with the ESP8266.