This chapter gives an overview of ferrofluids and their applications with a special focus on transducers development. It presents a novel strategy implementing a suitable noninvasive methodology to sense perturbations imposed on a liquid medium contained in a beaker. The chapter presents a tilt sensor, which exploits a ferrofluid oscillating in a resonant regime to prevent the mass adhesion on the housing structure. The size of the particles makes the difference between two main kinds of magnetic fluids: ferrofluids, and magneto-rheological fluids. Small dimensions of ferrofluid particles make them attractive for developing new devices and methodologies for the biomedical field with diagnostic and therapeutic purposes. The device is based on the Rosensweig effect, which is exploited to generate spikes in a ferrofluid mass injected in a glass plate filled with deionized water. The inductive readout strategy exploits the variation of the planar coils inductance due to the ferrofluid motion.