Unfrotunately, Peektab doesn't work on iPad unless you jailbreak it.
If you need a parental control for the iPhone/iPad, McGruff SafeGuard (they have a Windows Parental Control system) released a Child Safe Browser app that is a look-alike for Safari, but provides a parent with full control of the categories of websites that can be visited.
You may remember McGruff "The Crime Dog" - Take A Bite Out of Crime - from your own childhood.
It also provides a summary of activity to the parent via email.
Check out http://www.GoMcGruff.com/browser