Holy crap, this is awesome!  It would be especially great for if you see a color somewhere you want for house paint or something...you could "scan it" and bring it to the paint store and say "match this color."

Exact Colour of a Leaf, Exact Colour of an Apple

A real life Eyedropper tool! This is awesome. A pen with a little censor that scans the color of the object you point it at, then you can write in ink that exact color, it's like the eyedropper tool in photoshop outside of the computer.