When the user wants to create a world, they simply stand in front of each obstacle, holding their iphone, and press an "obstacle in front" button or something like that. The iphone will get it's location and facing, and place an object in front of the user. The user can proceed to add walls, and objects of various heights. Then they can use the iphone's camera to get "textures" for the game objects. After that, do whatever you want with the new world. The iphone's sensors are more than adequate to give the user a great experience. They will be able to move around fully in the 3D world, looking at their iphone to see what's in front of them. This is just an idea to get someone started, getting over a big obstacle. After that, it's up to the developer. Thoughts? Anyone up for the challenge? Is the iPhone even this precise?