I have one of these VR headsets that you insert your phone into and you can use VR apps. The headset also has a feature for AR, meaning I can take out a part of it and the phone`s camera can record what I am looking at and overlap AR elements on the image. The problem is none of the AR tutorials I read show how to do the split screen style VR apps usually have.
Its called Cardboard SDK but appears that Vuforia integrated it in its core:
https://library.vuforia.com/articles/Solution/Integrating-Cardboard-to-the-ARVR-Sample
If using other AR libraries (EasyAR maybe) Cardboard SDK might still be usefull.