Some train tracks carry an electric charge to locate trains or detect blockages. This electricity can also charge a phone, as demonstrated by Ukrainian DIYers Pavel Pavlov and Aleksandr Kryukov.

Warning: No, no, no. No. Don't mess with train tracks.

Tracks carry a little less than 3 volts of alternating current. To harness it, lay a piece of metal across each rail and connect it to components that will convert the flow into direct current, stabilize it, and step it up to the 5 volts your phone needs.

So why not try this? Well, it would take a really long time to charge anything. Oh, and hanging around an active train line could get you arrested or killed. Most important, a bad circuit could fry your precious phone.