When it comes to privacy and saving user’s personal data iOS does a pretty good job. However if you want to beef up your privacy and want to password protect specific applications on your device then a new tweak called Asos can help. With Asos you can lock any app you want and require passcode or Touch ID based fingerprint scan before anyone can access it. The best thing about this tweak is that you can lock specific apps that have your private data while letting anyone use rest of your device without any restrictions.
You can set up a custom passcode for Asos as well as use the same Touch ID fingerprint that you use to unlock your iPhone. Asos comes with several useful options such ability for users to choose when the device should ask for passcode and more. For example, you can select whether the app should ask for passcode every time you open it, after a certain amount of time or only when the device is respringed.
Asos is built quite neatly and takes care of a lot of things on its own such as it passcode protects the preference page for Settings so no one can change your passcode or settings. It also hide the previews of the apps you have protected in the app switcher screen.
Asos tweak is compatible with iOS 8 and iOS 7. You can get it for $0.99 from Cydia where it is available under the BigBoss repo.