FragmentVR is a VR application for HTC Vive owners that makes use of the front camera to create windows onto your surroundings from within virtual reality. FragmentVR puts each view into a SteamVR Overlay so that you can create and view them while you are in any other VR game or app. 

Usage is straightforward: place the bottom tip of your right controller where you want a corner of the view to be and pull the trigger. Once 4 corners have been placed the view is created and remains fixed in place.

Upcoming Features & improvements: 

Multiple overlays
HTC Vive Pro support
higher camera framerate
Greater UI functionality