The prototype is covered in a fine scale texture consisting of cuplike microfacets. Do you know the dimples on a golf ball? The microfacets are like that, only closer together. They look vaguely like this:
The black marks in the image represent specks which are more (or less) reflective than the norm. If the light catches them just right, you'll either see a shadow or a shiny spot at that point. The researchers have only proved the concept with a grayscale image, which you can see in the demo video below:
This is a neat trick, but I'm not sure I'd want to use it on most documents and photographs. There are only going to be so many times where I'd want to make it difficult to see an image. Okay, it is more realistic, but a 2d phot was never realistic in the first place. This trick just adds a new faux appearance of reality to the existing faux appearance. It's like 3d video; the content ususally works fine without it.
But there times where you might want to keep people from viewing a document from an off angle. I could easily see this as a way to obscure a document so it can only be seen when viewed face on. But of course that's going to be an effective security trick which will last only until someone a software filter to correct for the glare.
And of course there's the prank value, but I'm not sure that market will be big enough.