NQ Mobile Vault is a free vault app, but the best parts of it require you to pay for their service, so unfortunately the free version is pretty watered down, but is still a useful secret folder app.
The in-app purchases are for access to the “break-in attempt monitor,” the “secure cam login” and the “fake vault.” This secret diary app allows you to buy them all independently, which costs more, or altogether, when you first download them for $1.99.
The break-in attempt is probably the best feature as it allows you to see who tried to break in to your storage vault by taking a photo of the perpetrator. You will need the front facing camera turned on for this feature to work ton this private photos app.
The secure cam login is also hidden and you will need to use the iPhone’s camera to unlock it by pointing it at a blank canvas or surface.
The final premium upgrade lets you create a fake account so any prying eyes will believe they’ve cracked your file storage open, but of course this has been created by you as a diversion. Users rate it 4.5 stars out of five, so it's pretty solid, and there have been no bugs or crashes reported.
The only slight bummer is that you can’t use this content locker on other apps, which would be handy, but maybe future upgrades will make it more versatile.
The usage display screen lets you see how much storage you’ve used for the various media files, such as vids and pics, and the vault displays images in a 4x4 portrait view, with the premium features page listing how many break-in attempts you’ve had.
All in all, if you want to stop strangers from sneaking a peak at your personal stuff, then this security app has to be virtually uncrackable, so it's definitely worth the few bucks to avoid any embarrassing or awkward moments.