A defibrillator system optimizes the timing and manner of applying a defibrillator charge to a patient based upon data provided to the defibrillator from a utility module or one or more external devices. A parameter module on the utility module provides the defibrillator with patient parameter information. Devices external to the utility module may provide the utility module with coaching data that the utility module may pass through to the defibrillator as a proxy to the external devices. The utility module may also provide external devices with patient data that the utility module may pass through to the external devices as a proxy to the defibrillator on a scheduled or other basis. The utility module may additionally provide a reserve of power to enable defibrillators to be used where power is unavailable and to enable defibrillators to deliver multiple charges more readily anywhere, anytime.