SafeEraser is designed to keep your personal information safe when you want to resell your old iPod touch 5. It can permanently remove all the personal data.
iOS Devices Data Eraser
> Permanently erase content from your iPhone 5S/5C/5/4S/4
> Works with Jailbroken iPhone friendly and also compatible with carrier-locked iPhones
Warning: iPhone "Restore" does not delete personal data! - From CNET