Very simply, it's a light that attaches to your clothing via a strong magnet.

WSJ: Everything Is Illuminated, Hands-Free

Every kid who watched Mr. Wizard (myself included) learned how to make a strong magnet with some wire, a battery, and an iron rod.

FORBES: Opening the Kaba Simplex Lock: Just How Easy Is It?

We have analyzed the apparent fix that Kaba has implemented in their combination chamber (the brains of the lock) to stop it from being opened by a strong magnet.

FORBES: The Kaba Simplex lock is only for "access control": Is that what FDNY Engine Company 65 thought?

For now, Western Europe remains a strong magnet.

ECONOMIST: One more push

Current designs for maglev trains rely on electromagnets, since nobody has been able to make a permanent magnet strong enough to lift the weight of a train.

ECONOMIST: Maglev trains