Material that emits light, but appears diffuse? How can I have an object that emits light (using an emission shader) onto other objects, but when rendered appears to be diffuse (or any other shader for that matter)?

In essence, I want one object to emit light that shows on other objects, but that only itself receives light from other objects (not itself). Is this possible?

I tried doing this using Max/Add Shader nodes, but this just mixed in the "pure white" emission shader look with the diffuse shader I was using.
Use the Is Camera Ray output of the Light Path node to mix the shaders.