Samsung introduced in 2012 the feature called Smart Stay technology. The feature keeps the screen on by detecting via front-facing camera to determine if the user is looking at the screen. This feature is included to the Galaxy S3 devices, and it is not based on whether the user's eyes are closed or not.
There is a rumour that two new eye-tracking technologies will be featured in the upcoming Galaxy S4 called Eye Pause and Eye Scroll. The speculation about the Eye Pause is any video playing will go into "pause" if the user looks away from the screen, which would be convenient for those who don't have to push or click anything.
For the Eye Scroll, the interpretation is rather numerous. The primary thing about feature is it will allow the user to scroll through Web sites or apps by looking at the bottom of the page, removing the touch requirement just to scroll down. It also goes the same for other directions, such left, right or up.
Although eye tracking technology is not new, variants and improvements about it provide some accuracy to devices. Windows 8 is holds the most accurate eye tracking technology navigation, thanks to the Tobii Rex.
For a phone owner whose unit is not Galaxy S3 but has an Android smartphone with a front-face camera and wants to experience the Smart Stay feature, he can try some applications available in Google Play.
Smart Stay EX Lite by Elnware.com features double checking for preventing screen off, idle time, low light support, exception list for apps, debug mode if something goes wrong, and time out customisation.
SmartStay EX from nebkat is another app which features Android 2.3 support, customisable checking frequency, while SmartTimeout only scans when the screen is about to turn off, low light mode, exception list as well, and continuous mode that scan for a few seconds instead of taking a single image.