I know that the openParentApplication api in watch kit extension can open the host app in the background but not in the foreground.
I also tried using <
As of Beta 3 of iOS 8.2 it is currently not possible to open iOS app to foreground.
As you said openParentApplication can open app in background. Unfortunately there is no sign of API to open app on iPhone.
Multiple posts on Apple Dev Forums mentioned that it's not possible
https://devforums.apple.com/message/1076125#1076125
Correct, a notification can still declare a background action that the iPhone app will handle, so in that sense it can launch the iPhone app. But the iPhone app cannot be brought to the foreground by a WatchKit app.
And other post
https://devforums.apple.com/message/1082620#1082620
On a device, it[Watch app] will not - bring your iOS app to the foreground.