iOS基于位置的增强现实工具包/框架

is there any good free location-based augumented framework/api/toolkit for iOS? I tried Layar, but you can't change pretty much anything in the player itself so it's not worth much for me, I want to be able to alter the GUI for my needs. I also tried PanicAR from doPanic and the free version has watermarks all over the place. So again, is there anything else for iOS that is usable for free app if you want to alter the GUI yourself? is there any good free location-based augumente