Hand grip strength is a critical biomarker for assessing muscular function and rehabilitation progress, but existing measurement systems are bulky, expensive, and confined to clinical settings, limiting accessibility. We report a portable, low-cost monitoring system using a soft spherical device embedded with a highly sensitive, scalable multiwalled carbon nanotubes (MWCNTs)-enhanced electrospun thermoplastic polyurethane nanofiber sensor. The sensor exhibits a 600% relative current change at 10N load and maintains stability over 500 cycles, enabling precise grip assessment. Integrated into an elastomeric ball, the system wirelessly transmits data via near-field communication, allowing real-time smartphone monitoring without batteries. Results confirmed reliable detection of inter-hand strength differences, demonstrating clinical applicability for rehabilitation and home-based care. This scalable, user-friendly platform bridges the gap between lab-grade sensing and practical rehabilitation, offering a versatile solution for personalized biomechanical monitoring.