The camera that came with mine, (door prize)  is quite a fish eye.  Put it on the back of the grain cart.  Helps see the traffic, but the cars are really small and get big quit fast, because of the fish eye effect, so you have to watch it closely.  Works well at night. 

Neighbor mounted his to look into his semi when loading.  Lacks depth of field and was not that much help he said. 

Enjoy.