This hint details how you can swap the Command and Option keys on the Logitech K800 lighted wireless keyboard. This hint is necessary because the K800 does not respect the Modifier Keys settings under System Preferences » Keyboard.
To accomplish this you will need an older utility, a previous staple before its functionality was incorporated into the Keyboard pref pane, called Double Command.
First, download and install Double Command. Then, go into the Double Command pref pane and specify 'Command Key acts as Option Key' and 'Option Key acts as Command Key.'
Now, and this is the backwards-seeming part (Necessary if you have a portable. Otherwise, you can skip.) Go to System Preferences » Keyboard, and select 'Modifier Keys...' In this dialog box, use the pulldown to select your built-in keyboard on your laptop, and configure the Option Key to act as Command, and the Command Key to act as Option. The reason for this last step is to restore the normal behavior of your laptop’s built-in modifier keys.
[crarko adds: I haven't tested this one.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20110113215328810