We have used door alarms for several years. Our kids are now teens. Taz has it figured out. He knows if he opens the door quickly, he can shut it off and we won't wake up. These are just the type that stick to the door frame. He took the battery out too. So I have a new source: My Precious Kid. They have a door alarm that has a key pad. The sound can only be shut off using the code. I just ordered one for his door and one for his window as we also have problems with him going out the window once the weather is nice.
There are several reasons for door alarms. Taz gets up and raids the frig and fills up on refined carbs at an alarming rate...an entire bag of tortillas, a half gallon of ice cream. They send his mood through the roof. When he was younger we also had the problem of him going around and waking up siblings intentionally.
If you have never used alarms and are concerned about it becoming a game, there are some things you can do. Nancy Thomas gives her kids an hour nap for every time it goes off because she is tired and needs to rest. You can also have them do some of your chores since you will be tired.
P.S. Linda just told me about one at Radio Shack. It is cheaper with a key entrance if you'd prefer that!