I'm trying to get my application to be the only thing a user sees when the machine is powered on - like a kiosk, but a little more secure. Ideally, what I'd like to happen is this:

• At machine power-on, the user sees the Ubuntu splash image, then my app.
• While the app is running, the user can't get back to the desktop or a text login prompt via any keyboard shortcut. This is the (relatively) secure bit.
• When the user exits the app, the user sees a shutdown image, then the machine powers off.

In particular, I'd like to configure things so that the user never sees the Gnome desktop on startup or shutdown. At the moment, I've configured a default user to be logged on automatically, with an autostart item which starts my app, but after the Ubuntu startup screen the user sees the Gnome desktop briefly before my app is started. When the app is exited, the user is taken back to the Gnome desktop and has to shut the machine down manually.

Also, because of time constraints, I can't really start over with a different window manager.

Is there an easy way to configure all of this?