The e-ink used is the same stuff that powers the Kindle e-reader, but in this instance it’s been “ruggedized.” How rugged? Founder David Coelho tells OZY that ShiftWear Classics (which come in three different cuts) are waterproof and machine washable with soles made from Kevlar. And they have an equally impressive power source: walking. Every step you take recharges the tiny built-in batteries.