Safe Turn Indicator is an Australian invention that aims to make riding a push bike that little bit safer. You generally (well you should) use arm signals to indicate when you’re about to turn, what Safe Turn Indicator does is detect your arm movement and then flash like a regular motor vehicle indicator. According to the manufacturers, it offers these advantages:

• You do not have to learn to use the device, as its use can be combined with your normal hand signals
• To accommodate for your individual preferences, the base can be adjusted at 15 degree
  intervals to allow the tilt switch to function at any angle
• Containing 3 LEDs, the indicator is extremely visible and it flashes in a similar fashion as a vehicle/motorbike indicator does
• The Indicator is portable, lightweight and has low energy consumption
• The Indicator will keep blinking as long as your hand is raised
• The Indicator promotes safe cycling

The retail price is $19.95 AUD, more info over on the Safe Turn site.