This article describes a very interesting, albeit slightly pointless body modification. By implanting a magnet into one of your fingers, this artist could give you the ability to "sense" electromagnetic fields nearby. You could tell which electrical cables were live just by moving your hand nearby, or tell which speakers were magnetized in the same way.
It's really cool, so definitely read the article. I don't see too many real-world applications for this, but there might be someday, when it's perfected. I almost want one...