I got a Safe Turn review unit and promptly lost it. We moved after Thanksgiving, we're empty boxes and look what showed up! I finally found the Safe Turn bicycle turn signal.
The yellow flashing LED is mounted to a wrist band that you slip onto your wrist. A position sensor detects when you lift your arm to signal a turn to activate the flashing amber LED.
It's a clever idea and it works well. The position sensor is adjustable. You turn the light on and off by pressing the top of the lens down, and a activation delay ensures random hand motions won't set the blinker on. It's almost magical how well it works. The designers obviously put a lot of thought and testing into the design of the Safe Turn turn signal light.
Drawbacks: the light isn't bright for daylight use. The LED is powered by a pair of LR44 button cells that are not available as rechargeable batteries, though given the size constraints I'm not sure there's a good solution to that problem. Since I'm a multimodal commuter, I throw everything into my bag when I'm not riding, resulting in the lamp getting turned on and off all the time, which means I drained the batteries in about a week of riding. A friend of mine with a similar commute just leaves the Safe Turn light on his wrist for his entire trip to avoid that problem.
There's a USA distributor, but the easiest way to get this light is directly from the manufacturer which accepts PayPal and ships internationally. About $19 plus shipping, order fulfillment is very quick. SafeTurn.com for more information and to buy.