Samsung Galaxy S4 unveiled in New York TECHNOLOGY giant Samsung has unveiled its new smartphone - a handset that allows users to control the screen using their eyes. Experts say the South Korean firm's Galaxy S4 could outperform the iPhone 5, after the company took its battle to Apple with a dazzling launch on its rival's home soil. The gadget-packed device -which can detect when its user is climbing stairs - is expected to pose the greatest threat yet to the iPhone. The S4 was unveiled late on Thursday night at New York's Radio City Music Hall and only announced at the last minute to ensure secrecy. Critics have lavished praise on the device, citing its solid build, high pixel count and 5in screen size. Its headline features include eye-tracking technology, called Smart Scroll. Experts say it uses the phone's camera to lock on to the motion of the user's eyes, following wherever they move. The phone, they say, will tell where the user is looking, allowing it to respond to a certain set movements, such as to scroll a web page up and down, or a long, purposeful blink to click. Samsung's Smart Pause works in the same way: when the eyes are not focused on the screen, video is paused. A separate attachable accessory, called the Game Pad, similar to a wireless XBox controller, is expected to be in huge demand. According to a report from Experian Hitwise, the S4 is the most searched phone ever, despite not being released until next month. Ernest Doku, a telecoms expert at consumer company uSwitch, said the S4 had "more than" lived up to its hype and would have "worried" Apple. "They have taken the fight to Apple's back yard," he said. It was October last year when the iPhone 5 came out, so presumably it will be a little while before we see their rebuttal. Scott Hooton, chief commercial officer at Phones 4u, described the build-up to the S4"s arrival as "astounding" and said interest in the device had been 40 per cent higher than it was for its predecessor, the S3, in the first 48 hours. Carphone Warehouse said it planned to extend opening hours at its larger stores to cope with demand for the S4, and "inspire many people to make the switch to Android from other operating systems." However, some observers expressed doubts about some of the S4"s features, such as technology that lets the user change music tracks or accept a call with a simple wave of the hand. Stuart Miles, founder of technology and gadget site Pocket-lint, said the S4 offered "an incredibly powerful handset" that would sell well but added: "A lot of people will get baffled and either not use half of these things or be frightened by them because it may not be intuitive." Samsung is said to be expecting sales to be as high as ten million per month, largely driven by its new features. The S4 will be available through 327 mobile operators in 155 countries. The UK release date is 26 April. Stunningly bright and vivid ... a powerhouse under the hood, which makes it a promising platform for next-gen mobile games development. It really is ludicrously crisp and bold, and text is sharper than you'll see on an S3 [Samsung] or an iPhone. Nate Lanxon, Wired A mindboggling array of features and market-leading specs ... more detail than the iPhone in a bigger screen. Rich Trenholm, cnet.co.uk One of the best smartphones we've seen. But ... somewhat dated next to the aluminum and glass frames of the HTC One and Apple iPhone 5. Esat Dedezade, Stuff.tv