App Switch is a small utility app that is ment for mutiple display users.

When utilising the Command (⌘)+Tab function, your mouse will automatically set it self to the middlle of the screen in which that application is open in.

For e.g. you are working with Safari in the main display and you switch to iTunes (via ⌘+TAB) which is on a secondary display. The mouse will move directly to the middle of the display that iTunes is open in.