Big-screen smartphones may be the fashion, but how about two sizable screens on your next handset with negligible battery impact. SlashGear caught up with E Ink at IFA today to check out the company's latest prototypes, intended to spur some imagination among potential hardware partners. The mockups have a working e-paper screen filling the back, and a (non-functioning) LCD up front, offering two ways of displaying content simultaneously. And, while these might be concept devices right now, E Ink confirmed to us that there's at least one vendor looking at using the idea. Read on for a video demo.