The Image Fulgurator is an ingenious device that detects the flash from nearby cameras and quickly inserts a message onto whatever is being photographed so that it shows up in any photos being taken.
It operates via a kind of reactive flash projection that enables an image to be projected on an object exactly at the moment when someone else is photographing it. The intervention is unobtrusive because it takes only a few milliseconds. Every photo another photographer takes of an object at which the Fulgurator is also aimed is affected by the manipulation. Hence visual information can be smuggled unnoticed into the images of others.
Check out the results. (thx, red)