UPDATE: Pebble has released a statement saying it's working with Apple to fix the issue and has not been banned.
The full statement reads: "Still a work-in-progress, but we're working with Apple to clear up any misunderstandings to make sure rejections like the handful of recent ones don't happen again—they're being super responsive the concerns that bubbled up (much appreciated!). Apps are still getting approved with mentions of Pebble support in the description or metadata (e.g. RunKeeper). For now, developers should continue with their iOS app update plans and approval submissions to the iTunes store as normal (i.e. include Pebble support in your app info if that was your original intent)."
Apple has rejected an app from its App Store on the grounds that it mentions a competitor to the Apple Watch, the Pebble smartwatch.
According to the creators of the app, SeaNav US, Apple rejected it because the Pebble smartwatch, and support for it, were in the app code. This has been in the app code for two years but only since the Apple Watch appeared has it been an issue.
It is claimed that Apple has had this clause in its policies for at least four years. However other developers also claim they've included references which have never been rejected before, suggesting enforcing this rule is a new reaction by Apple.
The exact wording from Apple was: "Apps or metadata that mentions the name of any other mobile platform will be rejected."
In the details of that clause it says: "We noticed that your app or its metadata contains irrelevant platform information in the app. Providing future platform compatibility plans, or other platform references, is not appropriate for the App Store. Specifically, your app and app description declare support for the Pebble Smartwatch."