Is the companion iPhone app mandatory for Apple Watch apps? I am developing a simple standalone app for the Apple Watch. I really don't need any functionality on the phone. Am I required to provide an iPhone app?

The watchkit documentation is something like:


  Create WatchKit apps. WatchKit apps have two parts: A WatchKit
  extension that runs on iPhone and a set of user interface resources
  that are installed on Apple Watch. When your app is launched on Apple
  Watch, the WatchKit extension on iPhone runs in the background to
  update the user interface and respond to user interactions. WatchKit
  provides three opportunities to extend your iPhone app to Apple Watch:
  WatchKit apps, Glances, and actionable notifications.
Yes, a corresponding iOS app is required. The watchOS component is considered an extension by Apple and not a standalone product.

See Preparing Your 
App Submission for Apple Watch:


  App Review
  
  All iPhone apps with a WatchKit extension submitted to the App Store are reviewed based on a set of technical, content, and design criteria. Make sure to use our guidelines and resources before submitting your app for review.