Does iOS 5.0+ destroy data securely once deleted? Specifically if I delete a text message or an email from an iDevice, is said data destroyed to a point that data recovery would be unrealistic in practical terms? I understand that I can perform a full reset and doing so will erase data and restore the phone to a factory state but that is not my intention. My question is in relation to a device being used on a daily basis. This is a question of curiosity for the most part as I have been asked this by clients and I have not been able to point to a clear answer as of yet. I saw reference to this question but again it references a full restore and wipe of an iDevice with an APP and not daily use with no APP.
No, you need to wipe the entire device using the settings found under Settings > General > Reset > Erase All Contents and Settings. Simply deleting items from iOS applications does not provide any kind of secure deletion, and those files can easily be recovered (although that will be harder and harder as those blocks get overwritten in time).
This provides a one-pass secure delete call that can be liked to OS X's "Secure Empty Trash." While most 3rd party software won't be able to recover your data, government units have far more sophisticated tools that can retrieve data from far worse cases (even physically damaged storage).
This feature was introduced in iOS 2.0 and you can read more about it over at AppleInsider.