My Little Password is very simple app created by +François Beaufort that allows you to password protect any file from within Chrome OS.
I would consider this a simple low level security solution for sending a file over email or USB to someone who know the password already. The user could open the zipped file from within Chrome OS and insert password to view the file.
In all honesty the primary app I would use in this use scenario is MiniLock but there may be cases of needing some security and the end user is not part of the Google ecosystem. I think this is where My Little Password can come in handy.