vlfeat-ios This is Vlfeat running on IOS and includes a simple demo with 'vl_solve_linear_system_2' that will run on your iphone. Vlfeat is a computer vision library at vlfeat.org.
The code is a fork of an old version youngdueks ios-OpenCV-interface which happened to include vlfeat for iOS but has since been removed. Note, even though some of the folders have the word OpenCV in them, there are no OpenCV dependencies.