These smart shoes could be the answer though, as boffins at the University of Wisconsin-Madison have developed a pair of trainers capable of recharging your phone as you walk.
Dubbed InStep NanoPower, the new "bubbler" tech makes use of the kinetic energy generated by repeatedly putting one foot in front of the other.
The shoes use a high-tech sole fitted with a pair of flat plates separated by a small gap filled with a conductive liquid.
They're capable of creating up to 10 watts of power per square meter walked - more than enough energy to charge your 2 watt requiring phone.
OK, sure, they're not the most stylish of kicks and they feature a platform sole that would bring Tom Cruise up to an intimidating height, but they're a starting point. A sign of the walking, charging future.
Sadly, with the prototype tech having yet to be commercialised, you can’t actually buy them.