There is none for unjailbroken devices, to my knowledge, but there is one for jailbroken devices, a tweak for SBSettings called Hide Icons, it doesn't necessarily lock them but it hides them from your home screen and the only way to bring them back is to go into the SBSettings and slide the button to off to bring back that certain app.
That's all the I know of for locking icons and preventing anyone from using them