ha! might as well have the headline: '12th class student charges his phone from thin air' and then reveal in the article it is just made by placing a battery in thin air...
i'm guessing (backed up by the photo) that his proof-of-concept is literally a generator in the shoe hooked up to an attached bulb, so that when he walks a bit the bulb lights up.
It's Latin for "with." It's usually used with hyphens to describe something with dual purpose, so it would be more appropriate to spell it "shoe-cum-charger." It's also used in purely Latin phrases like magna cum laude.