Told you so. Google has released Cardboard SDKs for Android and Unity. The SDKs make it easier for people to develop applications for Google Cardboard. And unlike its competition, the low price point of the Google Cardboard will hopefully bring in anyone who is looking to start developing applications under a budget.
You can get more information and grab the SDK for yourself over at the official Google Cardboard Developers page. There they have the needed Android and Unity SDK as well as other information and downloads. Google even has a section for beginners who want to try developing in VR.
Image Credit: Google