NomadPlus ($40) is a smart backup battery that sits between your phone’s charging cable and the wall wart itself, letting you slide the white pronged square into its black body and connect your charging cord to the other side.
Plug it into the wall, and once it’s done charging your iPhone, it’ll fuel up its internal 1500 mAh battery, giving you a 70% additional charge when you need it the most without forcing you to use a bulky battery case or carry around an extra power brick.