The summer infant baby touch will scan between up to 4 cameras automatically and play audio from each room. Some other cameras will do multiple rooms but you have to manually switch or you only hear audio from the "primary" room. I think the newest version is the Baby Touch Plus or something like that but it is pretty similar.
Re: **Recommend your dual-screen Video Monitor**
BFP #2 7/18/11 - EDD 3/29/12 - Born 3/13/12
BFP #1 4/4/11 - Natural M/C - 7w1d - 4/30/11