Locktopus is a new applications that will let you password protect specific applications directly from the springboard.
After creating a password in Locktopus, you will be able to protect an application with this password by tapping and holding the app icon and wait until they start wiggling. Then tap the little “lock” badge on the app icon. Next time you try to launch this app, it will ask for the password.
Locktopus is available in Cydia for $2. I haven’t tried this app so I don’t know how it compares to the free LockDown app, which basically does the same thing. If you try it, please let us know how you like it.