iPhone "Restore" does not delete personal data! - Warning From CNET
If you're selling your iPad or passing it on to someone else, the first thing you'll want to do is make sure they won't have access to any of your personal data. Wipe everything from your iPad: contacts, messages, photos, videos, apps, account info, passwords and other personal data stored on iPad.
iPhone Data Eraser, Wipe iPhone Remotely, Delete iPhone Data Before Selling
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iPhone 5S, iPhone 5C, iPhone 5, iPhone 4S, iPhone 4
iPad Air, iPad mini, iPad with Retina Display, The new iPad, iPad 2, iPad 1
iPod touch 5, iPod touch 4