Carbon footprints are difficult. They’ve received a lot of attention in the press, and they’re firmly stamped (no pun intended) on the public psyche, but they’re not actually very accurate. Given the complexity of power generation in modern life, it’s something that’s incredibly difficult to calculate, and very easy to underestimate.

This device, the Carbon Hero, was designed by an art graduate named Andreas Zachariah. It tracks your phone signal, and if you’re moving at train-ish speed, on a train track, then it assumes you’re on a train, works out the distance you travel, and gives you a number for your carbon footprint. Simple, right? Well, there’s about a billion things wrong with the idea…