OpenGL Context from Plugin

I would like to find out how to place OpenGL calls in a Xcode plugin which will allow me to do things outside of Unity3d's SDK. Mainly the following:

1) I would like to listen for glXSwapBuffers so that I can perform a glReadPixel thus grabbing the screen without worrying about marshalling. I have read and have tried to find where to get the screen buffer efficiently, but haven't found anything fast enough yet.

2) I would like to make my own full-screen calls, hopefully being able to then full-screen the application on the monitor I choose rather than being forced to always full-screen to the primary window. - And yes, I know that you can move the "configuration dialog" to the monitor and then open, but I would like to be able to switch monitors at run-time without restarting.

3) I would like to place my own rendering on top of Unity3d's rendering.

I believe that at least some of this is possible as I saw several questions about rendering contexts and OpenGL in scripts, but I am unsure about how to go about this.

I'm using glBindTexture with the Texture.GetNativeTextureID() from a native plugin, and that's all I managed to pull off.

That only works for standalone players - you have to be in the forced opengl mode.