Chameleons are fascinating. Their ability to change their color quickly to either match their background or communicate with others is, well, unparalleled in nature. (They aren't the only creature that changes color, but they're the best at it.
Researchers now know how they do it (well, part of it anyway). Chameleons grow crystals under their skin. These crystals, presumably modified scales, can be expanded and contracted, changing the frequency of light the chameleon reflects. It's even possible they can reflect near-infrared light, i.e. heat, a useful ability in an endotherm. (What we still don't know: How the chameleons record their backgrounds to copy them).
Practically? We'll probably find that the chameleons make making these shapeshifting crystals look entirely too easy. However, it might well be that, at the very least, this is something that might show up in color changing clothing.
Or, better yet: Auto paint. Imagine being able to press a button on your key and change the color of your car. More practically? The ability to reflect near-infrared light might be very helpful to drivers in warm climates.