Session Expire Message

[eluser]ShoKatoo[/eluser]
I need a custom message for one of my apps. Normally, when one user loggs off I add a piece of flashdata that indicates that, and after the redirect to login page, based on that flashdata I throw a "you have succssefully logged out..." message.
My question: how could I throw a "you have been automatically logged off for security reasons" message?