So, for a long time, we've used the chime feature on our alarm to let us know whenever a door or window is opened in our house. This is particularly useful with small children in the house. Although we have tried hard to make sure that Rachel knows when it is OK to open the door and when it isn't (primarily that we need to know she is going to, at least at the front door), the chime helps us know when it happens... so clues us in if she forgets to tell us.
Occasionally we turn it off if we're going in and out or opening and closing windows a lot, because it can get a little annoying. A few weeks ago when we turned it off, we didn't turn it on for a while, and somehow we decided that if the alarm doesn't beep we have to say beep beep beep for it.
When we were at my parents' place for Thanksgiving, I had to go out to the car to get something, and when I walked out the front door, I said (not very loudly)... "beep beep beep".