That's like your bike's way of saying, "Back off, buddy!" It's there to ward off potential thieves and alert you if someone gets too close for comfort. Have you been considering adding one or just puzzled by how it works?Saw this thing and I've been puzzled for quite some time for not knowing what it is, then I just remembered how google can tell you what it is using a snap from your phone. What does it ACTUALLY do?
it's your car yelling bloody murder when something's wrong