Arduino is an Open-source electronic prototyping platform enabling users to create interactive electronic objects. Arduino boards come in a variety of sizes with differing features but all work off a similar microprocessor. Wi-Fi or ethernet connections are simple and you can monitor, or control, almost any electrical device in your home; lighting, heating, immersion elements, wall sockets, washing machine heaters, water pumps etc... Programming is relatively simple once the Arduino is connected to any PC (Linux, MAC or Windows) using Arduino's own language based on C++.
Data collected can easily be sent for web based storage and that data presented live for anyone to view over the internet. Web pages can easily be written so you can control your arduino connected home devices to run at your command, even remotely.

My new self-built home is extensively using this technology so to minimise my energy bills. It is another dimension beyond what 'Smart Meters' are supposed to offer in way of energy conservation.