CF mirror covers might be a cool way to add a turn-signal to our mirrors. If you are molding from scratch, you could incorporate a half-inch or so extra space on the bottom for a few amber LEDs.

I've been thinking that it would look really chic to use a translucent material like the stuff they make white plastic cutting boards out of. Put a layer of that with a few side-emitting luxeon LEDs embedded in the middle and you would a real nice uniform glow in 360 degrees. If you use enough LEDs you could even put a darkening tint around it so the white doesn't stand out when the signals are not blinking (although the white would look good on an ironman).

Just an idea that has been kicking around inside my head ever since I shined a laser on my cutting board and saw how amazingly cool it looked all glowing like that.