So what can we expect from this? The augmented reality is only displayed by a screen right? So when walking the street, do we need some sort of sunglasses to view peoples twitter feeds on their shirts? Would be cool!
You point your camera phone that has the Layar. or qr tag apps installed in your phone. You would then see the effects.
For marketing, imagine your company wearing a t-shirt that tells people to look at your t-shirt with the camera phone.