Having worked with a computer scientist in computer vision it is really interesting to see the huge difference between what people can imagine and what is actually possible. For instance, tracking people isn't a hugely difficult thing to do, but using multiple cameras to track people in 3d space is one of the hard problems of the day. Those kinds of things are possible in real-time, but doing facial recognition in real-time is nearly impossible. My favorite quote about computer vision comes from one of this professors PhD students:
3vr is one of the In-Q-Tel (CIA venture capital arm) supported companies doing a majority of the work for the NSA and looking their products is a good measure of what is currently possible.The thing you have to remember about computer vision is that everything is nearly impossible