We present a bio-inspired hydrogel magnetometer where the cell potential (V oc) between two hydrogels is used to measure an external magnetic field. Ferromagnetic particles located in the hydrogels move in response to the external field and change the V oc (sensitivity ~ 3.7 V T-1). As the field becomes larger than a critical field B c (~38 mT), these particles puncture the hydrogel boundary shorting out the concentration gradient region and abruptly reducing the V oc (sensitivity ~ 23.5 V T-1). In this regime, the V oc behaves similar to the neuron firing. In subsequent measurement cycles, the particles remain in punctured holes and the sensor behaviour is neuron-like with lower sensitivity (~20 V T-1). V oc also changes as a function of pressure (8 mV kPa-1) and temperature (2 mV K-1). After 4 h, the ionic concentration gradient diminishes in the device, and similar to biological cell fatigue, V oc decreases and can be recharged with many different techniques.