Signaling systems from Sonic Alert, Clarity, Ultratec and Bellman & Symfon can notify you to sounds in one or more rooms. They require signaler (receiver) and transmitter units. It is recommended that you do not mix system units from different manufacturers. Manufacturers such as Graco, Serene Innovations, Gentex, BRK Electronics and Krown have standalone units that notify for just one sound source in one room.