I won't take the time to explain what Augmented Reality is because, well, I don't know everything about it. But from what I can gather about it, you take a bar-coded image and when displayed through a webcam, using a specific program, it reads the bar code and interprets the information which will then output whatever 3D image it pertains too. You can give it a try here to help clear up some confusion.
As far as the tattoo goes why not consider the next gen augmented reality tattoos which allow you to have animated images appear from your limbs when viewed through a camera. Your boring 2D tattoo could turn into a gigantic 3D explosion that would make Michael Bay blush.
"These tattoos were developed and created by Think an App in Buenos Aires. The software technology recognizes AR bar codes on curved surfaces, the tattoo looks like a very simple and boring square until viewed through a camera."
The possibilities behind augmented reality technology are limitless but unfortunately is very costly to develop. With the proper funding, this technology should become mainstream and more practical, think expanding a PC screen into a real environment, virtual window dressings, posters, traffic signs. . .Sounds like something Steve Jobs would LOVE.