Plant hormones orchestrate critical physiological processes including growth, development, stress responses, and environmental adaptation, yet conventional analytical methods require destructive sampling and laboratory-based instrumentation that preclude real-time monitoring of dynamic hormonal fluctuations in living plants. Smart biosensor technologies have emerged as transformative tools enabling continuous, in situ detection of phytohormones through integration of biorecognition elements, nanomaterial-enhanced transduction mechanisms, and miniaturized electronic systems. This review examines advanced biosensing platforms for real-time plant hormone monitoring, emphasizing electrochemical, optical, and piezoelectric transduction strategies coupled with enzymes, aptamers, antibodies, and molecularly imprinted polymers as recognition elements. Nanomaterials including graphene, carbon nanotubes, quantum dots, and metallic nanoparticles enhance sensitivity, selectivity, and response kinetics while enabling miniaturization for wearable and implantable configurations. System integration encompasses signal processing circuits, wireless communication modules, and machine learning algorithms for automated data analytics. Applications span stress physiology, disease diagnostics, growth optimization, and precision agriculture, providing unprecedented temporal resolution of hormonal dynamics under field conditions. Critical challenges include improving long-term stability, achieving multiplexed detection in complex plant matrices, and scaling deployment across diverse crop systems. Future integration with Internet of Things infrastructures and artificial intelligence platforms promises data-driven decision support for next-generation precision agriculture and plant phenotyping.