DHT11 - Temperature and Humidity

This is a well known module used for measuring temperature and humidity and is often available packaged with an ESP01 as a complete solution. 

The DHT11 is one of a family of modules doing a similar function, recognisable by the protective plastic covering over the sensor. 

Data from the sensor is published to MQTT and the software can be loaded onto off-the-shelf ESP01/DHT11 modules to facilitate a common code base.