It "redirect the unused wasted energy within your device after your phone is fully charged. The app accepts, stores and releases this energy back into your battery upon request."
So it takes my fully charged phone, shunts that energy somewhere, stores it, then releases it. I propose a new name for a device that does that: a "battery." If it weren't an app, it would seem like just a weird backup battery, slowly shunting a little power from the main battery as you use your phone, so you never notice it's dropping faster than normal.
When your main battery is dead, poof, your backup battery dumps its charge into your main battery, and you're maybe not fully charged, but you've got a little life. Like driving around with a gallon of gas in the trunk, that's ultimately filled from the same service station nozzle as your main tank, but you won't be stranded on the roadside anymore when you main tank is empty.
But if there's no hardware in your phone for that, can an app do it? There are apparently lots of people/companies trying to develop true over the air chargers that 1) require hardware, and 2) don't rob peter to pay paul.