Kelly Hirano wanted to see how switching devices in his home on and off affected his electricity usage. Excited by the possibilities of reading the data from his SmartMeter, he discovered that he could buy a product (a Rainforest Eagle-200) which would expose the data via an API. Looking at their API documentation, he dug into the data using a Raspberry Pi Zero W and sent it out to a MQTT broker running Mosquito, as well as recording it locally. He added a Pimoroni Four Letter pHAT to the Zero to display the data. You can read a bit more over on his blog.