"Smart Hide Calculator" is a fully functional calculator app but with a little twist. Once you enter the password(u get to set it on first start of app and can also be changed in future) and press the '=' button then boom you are presented to an interface where you can hide, unhide pictures, videos, documents or files with any file extension placed in a folder on sdcard, and if your device have root you can also hide (freeze) and unhide (un-freeze) apps. more detail here http://mobotalks.com/mobile-apps/smart-hide-calculator-app-for-android-hides-your-private-photos-videos-behind-a-calculator/
