Lumus has long developed heads-up displays for the US military, but now it's using a developer kit called the DK-40 to bring its HUD tech to wearables outside the battlefield. The contraption's first stop was the CES show floor, so we couldn't resist putting our fingerprints all over it. The key feature of the DK-40 is the "optical engine", which eliminates the need for a thick piece of glass to house a substantially sized prism. For the most part, the lens is transparent, but refracting light can occasionally catch the prisms and remind you (again) that it's not run-of-the-mill eyewear. And as if one display wasn't enough, the firm says it's possible to add a second one for the left eye. Folks with eyesight issues can attach a pair of prescription lenses that rest on the nose grips, but the firm is also developing a version where the medically prescribed glass will be bonded to the lenses.