VR headsets like the Oculus Rift line can be expensive, but as "jamesvdberg" proves, they don’t necessarily have to be. In fact, a simple setup can be made for $80, using an Arduino Micro and an MPU6050 for control. Impressively, the project started out with an initial goal to build a device for under $150, but after some careful sourcing, James was able to cut this nearly in half.
The build mounts the Arduino to the front of a Google Cardboard-compatible HMD, which is wired up to the IMU attached to the side. A 5" Raspberry Pi LDC screen is inserted inside, and a modified USB assembly provides power and allows it to communicate with a PC to act as an inertial mouse. The net effect when the monitor is hooked up is that when you look up/down/left/right, your screen follows along, creating a very inexpensive VR rig.
One final trick here is that a program called Tridef 3D is used to split the output images into two eye sections for a stereoscopic 3D display. The “traditional” monitor is mirrored onto the headset for gaming, and an on/off switch is also implemented for when you need to use a normal mouse.