The opposite would be really good for designers - augmented reality of what a colour blind person would see. Would be good to check if your design is going to make life difficult for the colour blind.
There is a java app called Color Oracle that works on all platforms (http://colororacle.cartography.ch/). Turn it on and choose which color blindness to simulate.
I'm color blind and when switching to protanopia, the colors on my screen don't actually change for me.
