Is there a way to setup a web kiosk that uses the Opera browser, and is self resetting so that there isn't any chance that someone could hijack it?
A great way to do this would be to create a user (that automatically logins in perhaps) that has only read access to what is necessary. Then make 'opera -kioskmode' a startup application. Then remove ANY application not vital to your needs. If you really need to harden it further you may not want to start with Ubuntu-Desktop maybe Ubuntu-Server or Ubuntu-Core.