we have one in the house. basically as only one example....if I am watching tv late at night and all of a sudden the alarm sounds - if my wife is walking downstairs in the dark she can use the code word.
i am not going to shoot my wife if she forgets to use the code word, but it helps to minimize the chances for a tragic event. there are other instances too you can think of. a code word lets you and your significant other know everything is safe, it is just me, etc. I recommend having it for emergency backup
"Damn the torpedoes, full speed ahead!" -Admiral Farragut @ Battle of Mobile Bay 05AUG1864