The EcoMill is a curved, self-powered treadmill that turns your workout watts into actual watts so you can charge a phone or other gadget while you sweat. Your calories also run the display, which has all the normal controls you'd expect (pace, distance, time).
In addition to being greener than their electric relatives, self-powered treadmills offer a more intense workout since you have to push the belt with your own feet. Plus, they’re easier to spool up for intervals and there’s no top speed.
Made by Woodway USA, the EcoMill is not cheap. But the motor is guaranteed for life.