"Wearable technology." These days, the phrase conjures up images of laughably impractical watch-phone hybrids, single function devices like the FitBit and gigantic head-mounted displays that are useless for anything but watching movies for about 20 minutes at a time. But information leaking out of the shadowy inner test labs known as Google X indicates that the company is working on nothing less than a personal Heads-Up Display (HUD), a staple of science fiction for decades, and the goal of many converging technologies like transparent screens and microscopic transistors.