Basically, Safe Turn is a wrist mounted indicator light that automatically flickers to life whenever a cyclist raises his/her arm to signal a turn. In order to prevent the device from lighting during normal actions, like reaching for a water bottle or scratching the nose or ass, the device incorporates a "delayed start" feature that only allows the light to turn on if the user's arm has been in position for more than 200 milliseconds.
If you are one of the few cyclists out there that is courteous enough to use hand signals on the road, the Safe Turn may be a useful device—although it looks as though the guy in the picture may have waited a little too long. Available for US$18. [Product Page via Gizmag via Gearfuse]