I picked up one of these a few years ago to replace my wired door chime / doorbell system. Works like a charm. A bit on the expensive side, but you can attach all sorts of other gizmos like window and door security switches and extra push buttons. The nice thing is the strobe, so if anybody in your house is hard of hearing they can see when somebody is ringing the door bell. Installation was a breeze too.
http://www.honeywellstore.com/store/...door-chime.htm