There is a new 3D AR Engine for iOS available called Emcore3D , www.emcore3d.com. It is native, fast and lightweight, so no need to use the bulk of Unity.
There is a free trial available if you want to test it. Integration is super simple and it allows you to throw a 3D model into AR in no time.
Emcore3D features include - Multiple shaders per scene, optimised session and memory management, OBJ & FBX support, scale, shadows, proximity triggers.
You can even augment 3D models and environments with image, video and audio content - all served from your own CDN.
Download now at www.emcore3d.com
Why The World Needs A Super '3D-AR Engine'