Trial Period Expired

[eluser]skunkbad[/eluser]
I'm wondering if anyone else has ever implemented anything into applications they make that can disable the site even after FTP logins and control panel logins have been changed. I've been doing this by creating a "secret" method in one of my controllers, and if I browse to it and supply the correct argument, it basically overwrites the root index.php file with a message that says, "Trial Period Expired". I know it could be easily disabled, but I'm obscuring the code quite a bit so that it isn't easy to find. What are your thoughts?