The Apple Watch Ultra 4 introduces significant hardware improvements including a new S11 chipset, enhanced optical heart rate sensor with increased electrode surface area and photodiodes, extended battery life to over 2 days, and new health features like HRV trending and a Readiness Score system. The watch also promises upcoming features including a redesigned Health app with AI summaries, Health Age calculations, and additional audio intelligence capabilities, all backed by an Apple-conducted study of 1,400 participants.