I have a lot of data saved in my Android phone, but its built-in security is just miserable. Is there any data security app on which I can rely for my data's security?
You can use Folder Lock to lock the data on your computer. It has the possibility to lock all the content stored on your device. Visit Google Play to obtain the application. On a side note, there is another possibility which is more comfortable than Folder Lock and much safer. Install DropBox, synchronize your items on the cloud then assign a PIN to Dropbox and that's it. Everything will be locked and protected. The only requirement is the Internet connection that is needed to access the files but that shouldn't be a problem nowadays. You can install Dropbox from the same Play Store.