Over the last few decades, implantable defibrillators have become an established method of treating malign cardiac arrhythmias. There are some situations, however, in which it would be premature to implant a permanent defibrillator. In such cases, a wearable cardioverter defibrillator (WCD) can provide temporary relief and protect patients from life-threatening cardiac arrhythmias. Treatment with WCD is now included in national and international guidelines. Nevertheless, there are still some deficits in connection with WCD, especially regarding rescue chain optimization. For example, there is currently no telemedical link in place to emergency call centers and healthcare practitioners in the case of an event. Likewise, there are still some problems with rhythm analysis, concerning both shock delivery and cardiopulmonary resuscitation (CPR). These deficits are now to be addressed within the framework of MiniDefi, a project funded by the German Federal Ministry of Education and Research (BMBF). The concepts are described here for the first time.