Although you can't actually have eyes in the back of your head, the Werteloberfell ESUB Tracks Helmet is the next best thing. The German-designed helmet is equipped with advanced technology to monitor what's behind cyclists and when a fast car is approaching, integrated piezoelectric haptic actuators send out a warning to the rider. It also has a built-in microphone that controls a light on the back to indicate turns to other divers. The sensors are powered by organic printed photovoltaics wrapped around the helmet. They recharge as you wear it keeping the protective gear completely self-sufficient. For those who like to jam out as they rise, a pair of printed piezoelectric bone conduction speakers are heat pressed onto the leather strap and are designed to play music via Bluetooth without blocking out your surroundings.