If you need to hail taxis a lot, here's "Yo, Taxi!," a design concept by Terence Arjo that uses a row of LEDs and persistence of vision to give you an instant "Taxi" sign every time you raise your arm. The idea is to embed the LEDs into the sleeve of a coat, and when you wave your arm in that time-honored taxi hailing gesture, the LEDs automatically turn on. As you move your arm back and forth it gives cabbies the illusion of the word "Taxi" hanging there in the air next to you.
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If anyone actually gets around to building this device, we'd like to be able to change the text, where it might come in handy in traffic, sending certain messages to fellow drivers.
Yo, Taxi! [Clothes Make the Man, via Digg]