Use the Google Cardboard VR headset with an iPhone
"Of course, this being a Google product, it's exclusively for Android devices, right? Wrong! There are at least five iOS apps that work with Cardboard, all of them proof-positive that app developers may want to consider supporting the platform.
Want to see for yourself? For starters, you'll need the "hardware." Google's plans for a DIY Cardboard are readily available online, but you can also buy a readymade kit for as little as $20. For purposes of testing, I used one of Unofficial's Cardboard kits with my iPhone 5S. It worked fine, but I suspect a smaller iPhone (like the 4 or 4S) might actually prove a bit too small. If you're building a kit yourself, you can customize the dimensions to better fit a smaller screen."