Best feature: "DON’T WORRY ABOUT CHARGING - Optimized battery power lasts way beyond your shoe’s life." "Smart-shoes" with a dead battery are much more useful than an Apple Watch with a dead battery. Even so, they were able to prioritize this feature. I'm sure that compared to smaller wearables, they likely had a lot more physical space to work with to get the battery in there. I'd love to hear more from Under Armour about how they made this work.