Quite a bit has to come together to make this work! In the fridge is a temperature transducer, along with some stuff to transmit the values from it wirelessly every 10 seconds. A Raspberry Pi receives that and publishes to an MQTT server. Another process subscribes to that data feed and writes a row in a MySQL database somewhere. A Flask based Python application serves up a JSON representation of the sensor readings and some Javascript makes a pretty chart.
