Google's (NASDAQ: GOOG) Glass smart eyewear has been the product that has received the most attention in that still-emerging category. Yet as VentureBeat noted earlier this year, there are more than 16 kinds of smart glasses, many of which include SDKs for developers. Among the contenders is Epson, which last month announced an expanded developer program for its Moverio BT-200 smart glasses, along with a Moverio Apps Market to assist with discovery and distribution. Another player is Vuzix, which offers smart eyewear that emphasizes 2D and 3D video display capabilities. The company already has customers in the medical and construction industries. For more on the emerging alternatives in the "smart glasses" market, check out this FierceDeveloper special report.