Apple Watch is pretty much iPod Shuffle/Nano fusion with strap.
https://technology.ihs.com/389279/
https://technology.ihs.com/388837/isuppli-estimates-new-ipod-nano-bill-of-materials-at-4373
And a heart rate monitor and force touch and step monitor...
And NFC (for Apple Pay, magnetic card readers, etc).
And taptic interface.
And integration with your phone.
And new touch interactions with your friends/family.