If you’ve seen the third Harry Potter movie (or read the book), you probably remember the Marauder’s Map, which tracks the footsteps of everyone at Hogwarts. Kamin Whiteouse, a researcher at the University of Virginia, has turned that fiction into reality. Whitehouse said people want to know where everyone is in their home, so he decked out four homes in Virginia with sensors to track who entered what room and what appliances and utilities they used. That data was then sent to the “Marauder’s Map” companion app. The homes, which have been tracked for nearly four years, have sensors built into each doorway to measure the height of who enters a room. The rest of the sensors – anywhere from a few dozen to over a hundred – track just about everything else, like water and power usage. The study, which harnesses the power of the Internet of Things, aims to make us more aware of what’s happening in our homes and make smarter decisions about the energy we use. It’s also got the added benefit of being really cool.