2D object highlight

Hi!

I have GameObject with SpriteRenderer inside of it. It contains image with complex borders and trasparent pixels around borders. Is there any possibility to make this object highlighted (something like glow effect around borders)? I`v tried to use http://wiki.unity3d.com/index.php/Outlined_Diffuse_3 shader, but it makes gameObject fully filled by chosen color.

Please, help me to solve this problem!

you can have two images.

One without outline and one with outline.

Then, when you need to highlight, switch with the other image