With Beta 2 of the AppleWatch SDK, released last year, Apple introduced a new way for the WatchKit Extension to call the parent application (e.g. to send and request data). There are other ways for app and extension to exchange data – but this new way is the easiest so far (I think).
I’ve played around with the new method, googled some examples for help and put together a simple example of my own that shows how the whole thing works. In my example, I send a value from the WatchKit extension to the parent app and depending on what it receives, the app will send back a different string.
The example was implemented in XCode 6.2 Beta 5.
In the WatchKit Extension:
In the parent application (AppDelegate.swift)
That’s it. I hope this helps someone to quickly integrate the functionality.