The in-cabin market is evolving due to both new regulation and increased demands for improved passenger comfort. Specifically, recent regulations including “Euro-NCAP 2026 protocols for occupant monitoring” and “FMVSS 208 – Occupant Crash Protection – Seat Belt Reminder Systems” require a variety of measures to ensure reliable occupant detection, localization, and classification. Similarly, insurance in Europe (Thatcham in UK) requires the vehicles to be equipped with intrusion detection capabilities, and demands for enhanced comfort through targeted climate control and audio control require occupant localization. Current sensing modalities primarily address each in-cabin sensing task individually and have limited capability of covering other tasks. For example, a traditional sensor that can do in-seat occupant detection can not do intrusion detection. To cover multiple key in-cabin sensing tasks, namely intrusion detection, occupant detection, occupant localization, and occupant classification as child or adult, we present a single-sensor solution using mmWave radar with real-world implementations and demonstrations.