Fade Tool For Objects is a simple tool that allows to fade out and in objects between camera and player to the desired value.

It works with materials that use Unity Standard Shader only, and there are five different ways to fade the object.

Fade - Object fade out when it's obstructing the view. It returns opaque when it's not. Its shadow has the same behavior.
FadeKeepShadows - It works as Fade, but it always casts shadows.
Cutout - Object and its shadow disappear.
CutoutKeepShadow - Like above, but the shadow remains.
Transparent - It's the fade mode for transparent materials.
Opaque - The object doesn't fade, but you can set a color to highlight it when it's obstructing the view.

You can also set a color when the object is fading.

Fade Tool For Objects supports multi-materials objects.

If you want to try this script, you can download an example build that allows you to modify some settings on-the-fly.