The book provides an overview of different switchable electrochemical systems and modified electrodes. This area has developed rapidly and achieved significant progress. Electrode interfaces functionalized with various signal-responsive materials have been designed to allow switchable properties of modified electrodes. The book discusses different types of external signals that are able to modify electrode interfaces, for example electrical potential, magnetic field, light, as well as chemical and biochemical inputs. Multifunctional properties of the modified interfaces allow their responses to complex combinations of external signals. These are integrated with unconventional biomolecular computing systems logically processing multiple biochemical signals. This approach allows the biological control over electronic systems. Applications in different areas are covered, including unconventional computing, biofuel cells and signal-triggered molecular release in electrochemical systems. This interdisciplinary area is relevant for a broad range of applications in electrochemistry and materials science and is a must-read for scientists working with electrochemical systems and applications with signal-responsive materials.