GoKawiilApple Watch Series 12's compact Heart Rate complication now shows live readings
Apple's marketing materials for the Apple Watch Series 12 and Ultra 4 reveal that the small circular Heart Rate complication, previously just an app-launcher icon, will now display an actual live heart rate number. This upgrade is enabled by the new Health Sensing System, which measures heart rate every five seconds—60 times more often than earlier Apple Watch models. The feature does not appear on watchOS 27's release candidate for the older Series 11 and Ultra 3, suggesting it's tied to new hardware.