The second screen called the InkCase Plus comes with a 3.5-inch display, Bluetooth support and a built-in battery ready to offer 19 hours of continuous screen time, or up to seven days of standby time.

InkCase Plus is built with a high-density aluminium alloy frame shell and a hardened screen.

"The display is one of the thinnest and lightest on the market. You can view your vital information when you are enjoying sports and other outdoor activities," OAXIS said in a statement posted on its website.

Starting at USD 79, the device supports sports and fitness apps, photos and eBook content as well.

"InkCase Plus will let consumers personalize their phone case and allow alerts to be pushed to the low-power 'E Ink' screen," the firm informed.

The device, available on Android technology, can also display your favourite pictures, customizing your phone case according to moods and trends.