The Brains Behind the Image Fulgurator | Gadget Lab from Wired.com

The Brains Behind the Image Fulgurator

The Fulgurator lies in wait until an unsuspecting photographer takes a picture using a flash. When the device's sensor sees this flash, it fires its own unit, throwing up an image which is captured by the hapless photographer's camera while remaining unseen by the naked eye.

This is awesome and I want one. Even if the inventor does look like a caveman.