Samsung has unveiled the Galaxy S4 smartphone during a Broadway-style presentation. Here we take a look at some of its digital design and UX functions, including gesture-based controls driven by hovering your finger over the screen plus technology that tracks facial and eye movement, which could enhance the video and browsing experience on the device.

The world's largest smartphone maker introduced its flagship Galaxy S4 product with a 5-inch, full HD 1,920 x 1,080 screen at the event in New York City. The screen specs work out at 441dpi – or way beyond the ability of most people's eyes to distinguish individual pixels. Among the gaggle of new features in the LTE smartphone is a function called Smart Display, in which a front-facing camera recognizes eye and face movement to pause a video or scroll down a browser without touching the screen.

You can see some of the S4's new gestural controls and multi-tasking functions in action in the video above.

The Smart Pause feature can pause a video if a user's face and eye moves away from the screen.

"It understands that you are looking at the phone, and when it sees you looking away, it will pause," said Drew Blackard, director of product planning at Samsung, during an interview at the Galaxy S 4 launch event.

In a demonstration, a video paused when Blackard's eyes moved away from the screen and his face moved slightly toward the left. The video resumed when his face was looking at the screen.

The Smart Pause feature is only available for videos watched in the Samsung Video Player application, which includes titles from Samsung's Media Hub, which is an application that allows users to watch videos and TV shows. The Smart Pause feature can be activated or deactivated, Blackard said.

The Smart Pause feature won't work with video applications like YouTube, but the company is always evaluating opportunities and working with partners to bring new features, Blackard said.

Another related technology called Smart Scroll can scroll up or down a web page depending on a user's facial movement. A green indicator signals that the smartphone knows that the face is looking at the screen. Combined with the tilt of the smartphone, the browser windows will automatically scroll up or down.

Combined with facial recognition technology, tilting a browser is easier than moving the head up and down to scroll a web page, Blackard said, who demonstrated the feature.

"The reason why it's not my head up and down, it's because we've looked at that in the past and it's a jarring experience. Looking straight at the screen... is more natural," Blackard said.

The Smart Scroll also works to scroll emails, but not yet with applications like Polaris, which is an office productivity application for mobile devices.

The new technologies are part of a raft of new features introduced by Samsung so the smartphone could be used without touching the screen. The company has enabled gesture recognition technologies in which a hand can be hovered over the screen to preview news, email, files in a folder and information in calendars. Gestures can also be used to scroll in browser windows, switch between browser tabs, or even accept phone calls.

"We've done a lot of work in terms of discoverability and usability of these features," Blackard said.

Samsung hasn't announced a price for the Galaxy S4 yet but the smartphone will go on sale in just over a month in the UK, on April 26.