Kameraflage is a display technology that uses a special property of digital cameras to hide messages or other content in plain sight. The hidden content is only revealed when you look at it through your cellphone camera or other digital camera.
Kameraflage has some interesting applications that seem fairly practical (like having information appear only when a picture is taken at museums, etc.). However, I liked the more subversive element; kids (or grownups) who are stuck with a particular uniform can reveal another side of themselves to their peers with camera-phones. Note that the lightning bolt only appears in the camera-phone image in the picture shown above (see kameraflage sample photo).
I couldn't think of any real science fiction predictions of this, but it did remind me of the Vegans in Roger Zelazny's classic 1966 novel This Immortal:
Exposure to these stories is a must for cameraphiles: