Vault
Are you worrying about having your privacy invaded everytime your friends take your phone into their hands or you mistakenly leave it unattended in a coffee shop? Sounds like you need a real stringent solution to safe-keep your data from prying eyes, and Vault might just be your answer. It is one of the most promising data locker app on the Google Play store.
The app was created by NQ Mobile Inc., the developer that has churned out some of the most promising additions to the Android ecosystem. Coming from their stable, Vault is definitely a must have for the app drawer of your device.