1. A system comprising: at least one detector having a housing which carries at least one ambient condition sensor; control circuits carried by the housing, coupled to the sensor; and an audio input transducer carried by the housing, coupled to the control circuits, wherein the circuits include signal processing circuits, coupled to the transducer, the signal processing circuits cancel predetermined audio received from the transducer and output a processed speech signal which is coupled to speech recognition circuitry, the speech recognition circuitry recognizes selected speech to implement predetermined functions.