passwork protecting items inside the unlock passcode on iPhone

Is there a security app that anyone can point me to that will allow file security on the iphone. Something that only allows passcode access to say a photo folder, or an SMS thread?

I can't think of what they're called off the top of my head, but there are a couple in the app store that I know will create a password protected file for pictures etc.

If you're jailbroken, Cydia has some great solutions, too