Google on Friday is not only opening up Google Glass orders to interested buyers looking to score a pair of smart glasses, but it’s also rolling out a major update to its wearable device, bringing KitKat to Glass owners. Starting with 9 a.m. EDT, Google will be opening up a “limited number of spots in the Explorer Program,” but the device will only be available to U.S.-based customers willing to spend $1,500 for it. As for KitKat for Glass, Google describes it as its “most exciting” update for the device yet. “Our most exciting update is subtle, but big,” the company wrote on Google+. “We’ve been working on a significant upgrade to a new version of the Glass software. It’s not a