FragmentVR

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:

• HTC Vive Pro support
  
• higher camera framerate
  
• Greater UI functionality
  
• other HMDs + external camera support

The project is in early access release so expect there to be some rough edges.
In particular:

• Graphical bugs when switching from Standing to Seated tracking experiences
  
• Minimal/rough UI
  
• Suboptimal camera feed framerate

Your feedback is more than welcome. Check out our GitHub Issue tracker and Discord server to complain about bugs and request features (links in Early Access section above).
FragmentVR is only compatible with the HTC Vive for now since it is the only HMD with an accessible camera (HTC Vive Pro support is high on the to-do list).