In terms of big-name virtual reality headsets, we have the Oculus VR, Sony's Project Morpheus... and now Google has released Cardboard, a headset literally made of cardboard. Announced as part of Google's annual I/O developer conference, project Cardboard is "a no-frills enclosure that transforms a phone into a basic VR headset," says Google. You can download the plans for the headset, print them onto cardboard, and then build your own headset. It's then a case of placing your mobile device into the headset, and you're away. You will need a couple of specialized items to make it work -- two lenses, two magnets, some velcro, and a rubber band. Once you've build the device, you can then download a special app to test it out. The app comes with Cardboard versions of Google Earth, YouTube, Street View and other such demos. "Virtual reality has made exciting progress over the past several years," says the company. "However, developing for VR still requires expensive, specialized hardware. Thinking about how to make VR accessible to more people, a group of VR enthusiasts at Google experimented with using a smartphone to drive VR experiences." It adds, "By making it easy and inexpensive to experiment with VR, we hope to encourage developers to build the next generation of immersive digital experiences and make them available to everyone."