We have a VoIP app that can be installed on various Apple devices. Is there a way to transfer a VoIP call between devices like the Phone app? For example, on the Phone app I can make a call from my Apple Watch and then transfer that call to my phone and vice-versa.

We're currently trying to develop an Apple Watch companion app for our iOS app using the new WatchOS 9 which has the VoIP call capabilities. Is there a way to mirror VoIP notifications similarly to push notifications between the WatchOS app and iOS app? Essentially we'd like to be able to send a VoIP notification to the iOS app and have the answer/decline call screen show up in both the iPhone and Apple Watch. Currently when we send a VoIP notification to the iOS app, the Apple Watch does not receive anything. Push notifications and local notifications work just fine.