Getting the amount of triangles and vertices being rendered by the camera ?

I want to try something unusual. I want to change the camera clipping values based on the amount of vertices and triangles being rendered on the screen. My question is how can I get the amount of triangles and vertices being rendered and then referencing it in a script ? I know there is a way to get all triangles and vertices in a scene, but I only want the amount of the ones being rendered by the camera.