Wearable cardioverter defibrillator system, with a) main components of a wearable cardioverter defibrillator system configured to be worn by an ambulatory patient (82, 282, 482, 582) and b) a peripheral device (140, 340, 440) that is configured to be carried by the ambulatory patient, in which the main components comprise: an electrode (104, 108, 204, 208, 304, 308); a support structure (170, 370) configured to be worn by the ambulatory patient so as to maintain the electrode on a body of the ambulatory patient; an energy storage module configured to store an electrical charge, and to discharge at least some of the stored electrical charge via the electrode through the ambulatory patient; a main housing (201, 401); a main user interface output device (380, 480, 580) located at least partly within the main housing; a main communication module (290, 490); and a main processor (230, 430) configured to: receive an input about a condition, the condition being about one of the ambulatory patient and one of the main components of the WCD system, cause, responsive to the received input, the main UI output device to output a main human-perceptible indication (481, 581, 681, 781, 881, 981, 1081), the main HPI being about the condition, and cause, responsive to the received input, the main communication module to transmit an amplification signal (463, 1063), the amplification signal encoding a message about the condition, and in which the peripheral device comprises: a peripheral housing distinct from the main housing; a peripheral communication module located at least partly within the peripheral housing, the PCM configured to receive the transmitted amplification signal with the encoded message; and a peripheral UI output device configured, responsive to the PCM receiving the amplification signal with the encoded message, to output a peripheral HPI (442, 542, 642, 742, 842, 942, 1042), the peripheral HPI being about the condition. an electrode (104, 108, 204, 208, 304, 308); a support structure (170, 370) configured to be worn by the ambulatory patient so as to maintain the electrode on a body of the ambulatory patient; an energy storage module configured to store an electrical charge, and to discharge at least some of the stored electrical charge via the electrode through the ambulatory patient; a main housing (201, 401); a main user interface output device (380, 480, 580) located at least partly within the main housing; a main communication module (290, 490); and a main processor (230, 430) configured to: receive an input about a condition, the condition being about one of the ambulatory patient and one of the main components of the WCD system, cause, responsive to the received input, the main UI output device to output a main human-perceptible indication (481, 581, 681, 781, 881, 981, 1081), the main HPI being about the condition, and cause, responsive to the received input, the main communication module to transmit an amplification signal (463, 1063), the amplification signal encoding a message about the condition, and receive an input about a condition, the condition being about one of the ambulatory patient and one of the main components of the WCD system, cause, responsive to the received input, the main UI output device to output a main human-perceptible indication (481, 581, 681, 781, 881, 981, 1081), the main HPI being about the condition, and cause, responsive to the received input, the main communication module to transmit an amplification signal (463, 1063), the amplification signal encoding a message about the condition, and in which the peripheral device comprises: a peripheral housing distinct from the main housing; a peripheral communication module located at least partly within the peripheral housing, the PCM configured to receive the transmitted amplification signal with the encoded message; and a peripheral UI output device configured, responsive to the PCM receiving the amplification signal with the encoded message, to output a peripheral HPI (442, 542, 642, 742, 842, 942, 1042), the peripheral HPI being about the condition. a peripheral housing distinct from the main housing; a peripheral communication module located at least partly within the peripheral housing, the PCM configured to receive the transmitted amplification signal with the encoded message; and a peripheral UI output device configured, responsive to the PCM receiving the amplification signal with the encoded message, to output a peripheral HPI (442, 542, 642, 742, 842, 942, 1042), the peripheral HPI being about the condition.