A Wearable Cardiac Defibrillator (WCD) system is configured to be worn by a patient who carries a mobile communication device. The mobile communication device has a user interface that is configured to enable the patient to enter wireless inputs. The WCD system includes a communication module that is configured to establish a local comlink with the mobile communication device. The WCD system also includes a tethered action unit that has a user interface configured to enable the patient to enter action inputs. The WCD system can perform some of its functions in response to the action inputs or to the wireless inputs. Since the wireless inputs can be provided from the mobile communication device instead of the action unit, the patient is less likely to attract attention when entering them, and thus exhibit better compliance.