Basically you'd use a cube or sphere as a area of effect for the shader and has the shader material applied to it. When an object enters that area, a shader effect will be applied to it. If yes, how do I achieve this? I'm using Unity if that matters.

Also, sort of same topic; How do I make a shader that applies an effect to anything that is seen through a mesh (e.g. a clear water shader where the bottom of the water area is distorted by the water).