There have been two interesting Watch-releated links to make the rounds the last day or so:
Every major release of OS X and iOS has brought a revision to Apple’s HIG, and with Apple Watch, the company has spun off a new version of it just for the wearable.
Band Design Guidelines for Apple Watch »
Turns out, Apple is going to allow other companies to make Watch bands. This document is an interesting read, and be sure to check out the dimensional drawings for the two sizes of Watch.