It augments your sense of touch. I suppose this isn't obvious (however it seems obvious to me that many people would want to augment their senses).

Does it serve a practical purpose for me? No, I have it because it's "cool" but not at all in the same way that piercings are "cool." It's cool because I can feel motors, power transformers, etc.

It's also very useful for picking up dropped paperclips.