Cel Shading camera image effect

I am trying to apply an cel shading effect to the camera itself, however I am not sure how to go about doing it. The cel shading must be applied to the camera, since the effect must work on live video (from a webcam). I started with the "Edge Detect Effect" (which used the EdgeDetectX Shader) that comes with Unity, and it works well, but it's only part of the desired effect.

I tried using one of the Toon shaders that comes with Unity, but that doesn't work, I'm guessing that is used for real geometry.

Does anyone have any idea how I would do this? I don't really know how to write shaders myself, but I'm guessing that I would need to write a custom shader to achieve this. Any help with at least getting going in the right direction would be helpful.

Thanks