Use the Settings app on the iPod Touch/iPhone/iPad, go to General and tap on Restrictions.
The first time you do this it will ask you to set a 4-digit PIN. After you turn off YouTube and Safari (and whatever else you want) and exit the Settings app, then those Restrictions cannot be changed/disabled unless the user (your son or daughter, for example) knows the PIN you chose.
Now, install and launch B.O.B. for the first time. You will be prompted to create a 4-digit PIN (it can be the same as the one created for Apple's Restrictions or you can choose a different one). B.O.B. will NOT display any URL that is not already bookmarked, and URLs can ONLY be bookmarked by entering B.O.B.'s 4-digit PIN. Simple!
When the user enters an unbookmarked URL (or taps an unbookmarked URL on a bookmarked page), there are only two choices: (1) hand the iPod Touch/iPhone/iPad to a parent (that is, the ones who know B.O.B.'s 4-digit PIN) so they can enter the PIN that allows the URL to be bookmarked, OR (2) tap cancel and go back to the previous page (the unbookmarked page is NOT displayed).
The parent (that is, PIN holder) simply enters the PIN to allow the URL to be bookmarked. The parent can then review the page for content before returning the device to the user/child. If the parent finds the page unfit for viewing, they can open the bookmarks and delete the bookmark.
Bookmarks can only be added/deleted with the PIN. History can only be deleted with the PIN. B.O.B. is super simple and functions similar to Safari (except no site can be visited that is not bookmarked, of course!).
So, Apple protects the Restrictions you set with a 4-digit PIN, then B.O.B. protects what sites it visits by a 4-digit PIN as well! Perfect!!
I think you’ll find B.O.B. easy to use and completely secure (and our multiple open windows/tabs are better than Safari's!).
Note: PINs are easily changed if needed, as long as you know the current PIN. B.O.B. has a “Change PIN” button at the screen bottom when you are viewing the bookmarks of B.O.B.. To change the Apple Restrictions PIN, you have to “Disable Restrictions” and then “Enable Restrictions” to get it to ask you to set the PIN again.