Color-Changing Cell Phones

What if you had a cell phone whose body changed color based on distance from a location known as "home"? It shouldn't be that hard to make, technically: you've already got enough GPS-like information, and you could achieve the visual effect with translucent plastic and colored LEDs.

Would it be useful? I'm not sure: there are times when it would be helpful to know how far you were from home, or from some preselected destination. It sure would look neat. Maybe sometimes that's enough...