This app has the right idea but there are 2 major drawbacks. First there is no way to have the phone go to speaker when it makes the call. The phone ring alerts you but you cannot hear what is actually going on in the room. Second, even if you could listen and determine that everything was fine the app terminates when you hang up the phone. This means that for every false alarm you would have to go back into the room and reset the iPhone.
zfresco about Baby Monitor & Alarm, v2.5.1