Setting a lock code on your smartphone is highly recommended to protect your personal information, but sometimes a lock code can be a bit inconvenient.
What if you could do away with the device lock code, instead locking only the apps you want to keep private? An Android app named App Lock let's you do just that. That's not to say you can't use App Lock in addition to the lock code on your device, adding an extra level of security to your information.
App Lock, free in the Android Market, allows you to set a lock code or pattern on an app-by-app basis, preventing unwanted access to any app you deem private.
Setting up and using App Lock is a breeze.
(Source: Addictive Tips)