Apple Watch Series 12 and Ultra 4 have been on sale since September 18, and the Health Sensing System claim is already the product story: background heart-rate reads as often as every five seconds and a readiness score built on higher-frequency HRV. What has not shipped is Live Rewind and Siri Recap. Apple still lists those as a later-2026 beta, English first, and only on Series 12 or Ultra 4 paired with an Apple Intelligence iPhone. EU availability is excluded at the start. Buyers who treated the September keynote as a full software drop are still waiting on the headline watch features.