ARToolkit is a widely used open source platform, among other features it also supports superimposing of virtual images on live environment through a video or see-through display. Vuforia AR platform provides an ease of use where your applications can see wide variety of things such as objects (including user-defined), texts and markers. It also works well with Unity which is a powerful cross platform 3D engine. Writing a 3D engine is intensive work so these platforms allow you to use your existing 3D engines such as Unity by leveraging the platform SDK.
Keep an eye on the Google Tango and Microsoft HoloLens that are working on an AR, VR and Mixed Reality eco-system that includes AI, advanced gadgets like Fisheye & depth cameras and advanced sensory and perception devices. Tango is a platform that uses computer vision to give Android devices like Phab 2 Pro the ability to understand their position relative to the world around them – no longer there is a need to have multitude of beacons for geo position tracking. A Tango-enabled device has wide-angle fisheye camera, a depth sensing camera, accurate sensor timestamping, and an SDK that enables apps developers to use motion tracking, area learning and depth sensing.
See the full story here: http://www.cio.com/article/3169685/emerging-technology/augmented-reality-next-frontier-for-competitive-advantage.html