I'd like to know too!
My DDs are 4&6, they share a room and I don't think I'll ever be able to go without a monitor in there! LOL! Their room is right by the front door with a HUGE window and our bedroom is in theback of the house. When baby comes her room is right next to ours but we'll need 2 monitirs too.
I'll be curious to see the responses here. Thanks for posting the Q.