Shader tester iOS App? Will Apple reject an app which renders a 3D scene that allows you to modify and compile GLSL ES shaders by editing them in the app? (something not unlike e.g. http://shadertoy.com, but native OpenGL ES 2)

What about if it registers for a file type and opens .vsh and .fsh files as documents?

I know that it may be problematic if the app automatically downloads shader code from a server (and then runs it), but the answer is not so clear for these other approaches.
Shaderific allows you to "import shader files with Dropbox or iTunes Document Sharing" so they were allowed, but the bad news is that you have at least one strong competitor.