Providing temporary use of online non-downloadable software for processing, interpreting, monitoring, and managing data produced by a sensor system that measures, tracks or monitors brain activity and mental states; leasing of sensor systems comprised of a wearable modular sensing unit, namely, biofeedback sensors, optical sensors, and magnetic sensors and supporting modular electronics for data processing, signal processing, and connectivity, namely, computer hardware for the purpose of measuring, interpreting, tracking, and monitoring brain activity and mental states; leasing of sensor system, namely, modular electronic devices, namely, biofeedback sensors, optical sensors, magnetic sensors, and computer hardware for the purpose of measuring, interpreting, tracking, and monitoring brain activity and mental states