Requires iOS 4.0 or higher
Protect your folders with password. You can set a password via Settings.app for your folders. You can also Enable/Disable this tweak, and protect some of iOS functions like Spotlight and Multitasking.
Obviously you can lock Settings.app, so nobody can change your password. Set password confirmation via Settings.app
No icons are added to your homescreen. Tweak's options are configured from Settings.app
See further below for Screenshots