VRidge - Play PC VR games inside your mobile VR headset.
TrinusVR - TrinusVR connects your Android phone to your PC so you can play your PC games in virtual reality.
Virtual Desktop - Use your computer in VR
Cardboard Camera - The VR camera app for Google Cardboard that lets you share moments with virtual reality.
BigScreen VR - Your desktop in virtual reality, with friends; play games, watch movies, and hangout in VR.
Phone VR - Use Steam VR-enabled applications with your phone as HMD (Head-mounted display). The only Open-Source solution to similar commercial packages like VRidge, Riftcat, Trinus etc etc. (https://github.com/ShootingKing-AM/PhoneVR)