Ubuntu Security :: Checking If Anyone Is Viewing Passwords Stored In FireFox?

As I am a paranoid bastard, I made a bash screencap-script for my Ubuntu-computer, so I can check if anyone uses my computer for things I don't want them to do (eg. checking if anyone is viewing passwords stored in FireFox, looking at private files, or other things I find disturbing). There might be other people than me that is paranoid and want to monitor what's going on on their computers while they are away or letting someone else use their computer when going to the bathroom.

This is a small script, I'd like to hear if there is any improvements that can be done, so I can learn more and become better at such scripting.

The script requires Imagick (sudo apt-get install imagemagick) and a folder in the ~-directory (/home/username) called ".screen" (hidden, as this makes it more difficult to "intruders" to find it and it looks more like a system-folder than a monitoring-folder).

The script:

Code:
#!/bin/bash
i=1;
j=`date`;
user=`whoami`;

[Code]....

Add this script to /usr/local/bin and then go to keyboard-shortcuts in GNOME and add a shortcut-key-combination of your own choice for the script. Call it whatever you'd like, and the command you want to run is simply "screen". To add a shortcut for stopping the script, you add another shortcut-key-combination to the command "killall screen".

This enables you to monitor activity on your computer while you're away, saving png-screenshots of your desktop every three seconds in the folder /home/username/.screen/date.

NOTE: I'm not taking any responsibility for what you do with this script. Remember that monitoring someone's activities is never the right way to handle anything. Also, it's illegal many places. Take care and use it only for educational and testing purposes.