iPhone 6S battery drain is a worry that gives many of us restless nights. There's no need to fear the dreaded 1% warning anymore, however, as this iPhone 6S case means your handset will never run out of power again, Digital Spy said.

Stepping past Hogwarts-levels of wizardry, the AMPWare Case hides a small hand crank that lets you develop some solid wrist muscles while re-juicing your smartphone.

Connected to a small dynamo, turning the crank - which sits flush with the slightly bulbous, 18.5mm-thick case when not in use - generates power that is then used to recharge your phone.

According to the manufacturers, five minutes of vigorous wristwork will generate about an hour of life for your phone.

And as well as keeping your phone going all day, the AMPWare Case will protect your iPhone from knocks and drops thanks to a protective bumper surround.

Available in a trio of colours - black, bright green and olive green - the AMPWare iPhone 6S case is available now for $79.