Actually, depending on whom you ask, we have nine or more senses (the four extra are considered most often to be balance, temperature, pain, and kinesthetic sense). Some even say that our sense of taste is actually several different senses.
The point is there exists a neodymium magnet that, if implanted into the skin, can almost give someone an extra sense. The implant lets you feel electric / magnetic fields through what's been described as a buzzing sensation, a tingling, or an oscillation.
It was discovered when body modification artists Jesse Jarrell and Steve Haworth decided to try implanting a magnet into the skin to help carry things. It was unsuccessful, because as they discovered, the skin on top of the magnet died and the body rejected it.
But when a friend suffered an accident that left a shard of iron in his finger, they were given a new idea. Their friend worked with audio equipment, and he found out that after the accident, he could tell which speakers were magnetized from the sensation that passed through his finger.
Todd Huffman, a graduate student at Arizona State University, joined the project and brainstormed with Jarrell and Haworth about how to develop the implant and where to put it.
It was tested on the ring finger, and had a high degree of success. According to Huffman, the implanted magnet works by moving very slightly in response to electromagnetic fields. If you could have it implanted, would you?