One time I had done a little repair for some friends, so I was wearing my electrician's tool belt. I then got caught in a conversational knot, blocking the hall. I got bored with the topic, but it reminded me of something, so I interjected "Hey, did I ever show you my third-eye detector?"
This got immediate attention as I pulled an ordinary circuit tester from my pouch. It had an alligator clip on a wire, and a pointy tip on a small flashlight. If the clip touched the tip, or the two were connected by a sound wire, the light would go on. I clipped the lead onto my wire-frame glasses near the ear, and then slid the point down my forehead from the hairline, holding my hand low for easy visibility. When the tip got to the middle of my forehead, the side of that probe hit the bridge of my glasses, and the rig lit up. Immediate sensation! Everyone was taking a turn, clipping the wire to their ears, and stabbing at their foreheads.