With 3D-TV failing to become the next big thing in home entertainment, TV manufacturers are increasingly developing smart television sets capable of accessing video over the Internet -- ones that employ apps and remote devices to do so. According to market researchers IHS Screen Digest, more than 25 percent of all TV sets in 2012 -- a whopping 66 million -- were smart TVs, and the sales rate of such sets is surging. Screen Digest predicts that it will double to 50 percent by 2015 to 141 million sets. Despite a decline in global television shipments in 2012, consumer demand for Internet-connected televisions soared during the year -- and the surge in sales shows no signs of abating, commented IHS systems analyst Veronica Thayer in a statement. Smart TVs are rapidly joining the mainstream as manufacturers refine their products to add new features and to make them easier to use.