The convergence of portable health diagnostics and everyday consumer electronics represents a significant opportunity for preventative healthcare. The HEALTH-KEY ULTRA integrates nine distinct health sensors into an ultra-compact (48 × 18 × 9.5 mm) keychain form factor that doubles as a 64GB USB-C flash drive. Novel engineering contributions include: (1) the USB-C connector shield repurposed as a biopotential ECG electrode; (2) a co-axial Venturi breath channel housing both an electrochemical fuel cell and MEMS gas sensor for simultaneous BAC and VOC analysis; and (3) an autonomous dual-mode architecture switching between USB composite device and BLE 5.3 GATT server. The device covers 21 health metrics with a BOM cost of approximately $47.70. Patent Pending: US App. No. 64/073,334, filed May 23, 2026.