This project allows you to use electrical appliances on a 'pay-as-you-go' (PAYG) basis, using the IOTA tangle.
This is built using Flask and Flask-SocketIO, which allows to create a continuously updating web dashboard that the user can monitor. A QR code for the IOTA address is also visible in the webpage, which allows users to 'top up'.
Raspberry Pi 3, RS232 Power Meter.
https://www.hackster.io/yasaspeiris/payota-pay-for-what-you-use-d5f3b7
Building Smarter Cities (Organized by the IOTA Foundation)
Smart Energy: 3rd Place Hackster Impact Prize