Looking for good quality sound without the ugly speakers? The Amina Tech AIW-5 speakers go inside the wall itself, behind the plaster. They use NXT flat speaker technology to set up vibrations in a composite panel, which are transmitted through the plaster of the wall. The company claims the sound is good enough to be used as part of a home theater setup, with each speaker generating a decent 80 watts of power. You do need to tear out your walls to install them, but they'd be perfect if you are looking to drive someone mad. Why are the walls whispering and telling me to kill everyone?
AIW5 In-Wall Loudspeaker [Amina]