It works quite simply: Plug your iPhone 6 Plus (and, in the future, other smartphones) into the Smart Boy and it'll allow you to play Game Boy and Game Boy Colors cartridges. The Smart Boy is equipped with the standard Game Boy set of buttons, while the phone's screen is used to display the game. The Smart Boy has a built-in battery that can be charged by the phone; with a 6 Plus, gameplay is said to last for five hours.