I'm trying to make an alarm system and I don't want it to be limited by to few switches. Now I know everyone is going to say how many doors do you have that you want to put a sensor on. Well its only 3 so far but there are other things like outside gates, garage door, mailbox (then I can have my computer go "you've got mail" and it be real mail ... lol). I'm sure there are other things as well but thats all I've got right now. If i'm going to use up eight pins I might as well get as many switches as I can out of them.
The using a whole other pic might not be a bad idea. hmmmm