Cute Circuit’s Galaxy Dress – World’s Largest Wearable Display
24,000 color LED, plus a couple of ipod batteries guarantees you’ll stand out in the crowd:

24000 full color LEDs, measuring a mere 2 by 2 mm in size, were used to create this mesmerizing dress. The circuitry itself is hand embroidered on a layer of silk in a fashion that permits it to stretch, allowing the LED bedazzled fabric to drape with fluidity over the body.
To fuel the LED fabric, a few iPOD batteries illuminate the silhouette for 30 minutes to an hour.
Additional layers of silk chiffon diffuse the light, giving the gown a colorful jellyfish-like transparency .
When the digital patterns fade and the silhouette grows dark, more than 4000 hand-applied Swarovski crystals add sparkle and glitter to the gown.
Take a look at the dress in action:
Link and video from Syuzi at fashioningtech.com. Besides a very pretty pattern to display, a person could run a personalized message or potentially sell advertising space.

This would be horribly gaudy in practice. But also rad.