Open banking offers users a way to have easier access to their own bank account information, like via third-party applications. This is achieved by allowing third-party financial service providers access to the financial data of a bank's customers through the use of APIs, which enable secure communication between the different parties involved.

When I first considered how to make my "dumb" hot water tank smarter, the obvious solution was to buy a smart-connected immersion heater. However, being a tinkerer, I wanted something a little more DIY—and cost-effective! Enter the ESP32, a cheap and versatile microcontroller. With two of these boards and a little ingenuity, I managed to monitor my water tank’s temperature and energy usage. Here’s how I did it.