Based on the images SamMobile posted, launching PhoneCast takes you to a lakeside picnic area that serves as the screen's background. You'll be able to adjust the video's brightness and the display's size within its interface, as well, so you can customize the picture for your eyes. While it won't make every third-party video and streaming app compatible with the Gear VR, it will work with quite a lengthy list of programs:

Plex Vudu Epix Hulu Tubi TV Crackle YouTube NFL Musically Kodi Naver TV V Live Kakao TV Live Smart DMB Africa TV Naver Webtoon Oksusu Olleh TV Mobile LTE Video Portal VLC Xfinity Sling TV MX Player

PhoneCast is still in beta, so you won't find it in any app store, but you can download it from SamMobile's APK's store and install it on your device.