A flexible, lightweight and minimally intrusive monitoring system has been developed to assess animals' behavioral responses. The system consists of wearable composite magnets and magnetic sensors integrated into a miniaturized wireless communication module with a flexible battery. The shape and size of the NdFeB-PDMS composite magnets are highly versatile, while the magnetic and mechanical properties can be tailored within a wide range by the powder concentration. The magnetic field of the composite magnet is sensed by a 3-axial magnetic sensor, and the measured data is wirelessly transmitted using Bluetooth low energy communication standard to a smartphone and dashboard. To withstand corrosive environments and enhance the durability the composite magnets are coated with 2 μm of Parylene C, while surface passivation of the wireless module is achieved with 5 μm of Parylene C. The system has been implemented for real-time monitoring of crabs, giant turtles, and giant clams, indicating its potential for novel and affordable animal monitoring applications.