Two likely killer features to rollout with the iPhone 6 and the iPhone 5S are eye-detection capability and automated battery power adjustment, both designed to conserve energy and extend the handsets' operating hours.

In a patent application published last week, Apple is resurrecting an invention that allows future iOS devices to sense a staring eye and adjust to a corresponding function on the process, Patently Apple said in a new report.

The technology was first explored in 2008, the same report said, hinting too that prior to the smart eyes features introduced by Samsung via the Galaxy S4, Apple had already patented a similar invention.

Gaze technology, as Patently Apple termed it, was originally geared for television and when deployed to mobile devices, one of the core functions would be to automatically turn off unused smartphone or tablet features to conserve battery power.

When implemented, "gaze detection sensors such as a camera may be used by the electronic device to determine whether a user's gaze is directed towards the electronic device."

Apple plans to execute gaze technology in two operating modes: to achieve optimal mobile device experience and to prolong battery life.

The first function will complement popular iOS applications such as iTunes media playback that, for example, allows for smart video watching. With the technology in action, an iPhone will detect the gaze of an eye and will either pause or resume playback.

Also, the device will automatically shift in standby mode when not in use, the phone sensor again relying on the gaze of an eye.

"When the electronic device is operating in one of the standby modes, circuitry and components such as a display screen, touch screen components, gaze detection components, and a central processing unit or CPU in the electronic device may be powered down or operated in a low-power mode to minimize power consumption in the electronic device," the report said.

The whole function can also be suspended when the situation calls for it. "The device may suspend gaze detection operations whenever a sensor in a device indicates that gaze detection operations are inappropriate or not needed," Patently Apple said.

Such added feature ensures that the iPhone 6 is functioning with optimal settings plus the added benefits of avoiding energy waste.

While already in full development, there is no assurance that Apple engineers will be able to deliver the technology in time for the rumoured iPhone 6 release date, which analysts said would take place June 2014 or earlier.