We read through all of the documentation, Xcode 7 header files, and tried to summarize everything we could figure out about watchOS 2. We hope this is a quick jumping off point for developers who just want a quick description and links directly into the Apple documentation.
http://www.sneakycrab.com/blog/2015/6/8/watchos-20-tldr
Please give feedback, corrections and new discoveries, and we'll update the post with new information as we find it.