Is it possible to set restrictions on any iOS app? I want to put a passcode restriction on the Video app (and others), but the options I see in Settings are only for a few things. Is there a way, native or third party, to do this?
iOS only allows you to block built in applications and features, and age-rated apps from the App Store.

If you jailbreak, there is a tool for specifically locking apps individually called iProtect on the Cydia Store. However, it costs $8.99.