If your smartphone and your e-reader had a baby, it might look a lot like the YotaPhone 2. Combining the features of an Android smartphone with an electronic paper display on the typically forgotten backside, it's the world's first dual-screen smartphone. The rear e-ink screen is covered by a touch-sensitive, curved matte finish, and allows you to read, text, email, or tweet without even flipping over to the LCD screen. The rear screen stays on all the time, but uses way less energy and can hold a charge for up to five days. Practical use paired with imaginative design make it easy to see why some are calling this the smartphone of the future.