With ios7+ just activate find my phone in settings> iCloud and your iPhone is secure. The phone won't give out any information until either the phone screen look or iCloud password is entered. The tech savvy can reboot the phone, he can even goes further by putting the phone in DFU mode so to factory reset, but at the end of the factory restore, he will be ask to enter the find my phone password which will double check with apple server, until he won't be able to enter the right password, the phone will just be a solid brick for him. Save if you ever come to forget your find my phone password, unless you are the first owner of the iPhone with valid registrations, Apple won't help you to unlock the device.
Basically find my phone made any other security measurements useless from ios 7+ going as it's the most efficient security measurement ever by Apple, now for 5S and futures devices going on, there is the touch ID option as well, but this touch ID is only store locally in the iPhone and not on Apple server so it can be easily pass by anyone mastering the IPSW, but find my phone is another story till date is one unbreakable security.
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