Securely delete guest accounts in OSX
It's kinda possible. You can use a logout hook to run a script when a user logs out. This will also be run when the guest user is logged out, too. All you would need to do is create a script that SRMs the guest home folder when the Mac is logged out of or shut down.

This command will initiate a login hook (presuming that /usr/local/bin/logoutscript exists and is chmodded correctly so that the script is executable) 

sudo defaults write com.apple.loginwindow LogoutHook /usr/local/bin/logoutscript


You can easily write a shell script that would SRM the Guest account home folder.