Gizmodo had this link. It points here. And I want these.
I remember when I had my first contacts fitting. The doctor touched a piece of paper to my eye that released a dye into the tears. Suddenly the room became dark and brown. I thought would be awesome: touch the side of your eye, and release this dye that would act like sunglasses.
But now there actually the possibility of photo-changing contacts.
The only drawback is that you they won't help you stare at beautiful women without getting caught.