Turn by turn directions when riding a bike. Easy to track countdown timers that don't require swiping/navigating through a smartwatch UI.
Limited purpose devices are useful because the UI can be optimized to just a handful of use cases. Just like the original Palm Pilots were (IMHO) better for organization than modern smartphones. (The original Palm Pilots also had a more responsive UI and never decided to, at random, take 10 seconds to load my home screen after unlock.)
Combine this with Amazon's smart store that knows when you've put an item in your basket, and a shopping list. Have your shopping list appear one item at a time, and automatically progress to the next item as you fill up your basket!
No need to flip through the UI on a smartwatch to get to the shopping list, it just appears when you walk into the store.
