Unity's "Post Processing Stack" has more potential than you think. With this asset you can access the natural/realtime Depth Of Field effect for your camera.
Wherever you look, your focus smootly adapt there, LIKE YOUR OWN EYES!!
+ Easy to use
+ Mobile, WebGL compatible
+ 2 different modes (General Auto Focus, Object Focus)
+ Change focus speed to make more dramatic transitions
+ Focus a spesific object for elegant highlighting
IMPORTANT! This asset requires Unity Post Processing Stack