Current HealthKit APIs provide access to heart-rate data through queries, but not as a true real-time stream. This limitation prevents systems such as Mercedes-Benz ENERGIZING from dynamically adapting the vehicle environment — including light, sound, seat massage and climate — to the driver’s physiological state.
The ENERGIZING Coach developed by Mercedes-Benz uses continuous biometric feedback to enhance comfort, focus and safety by adjusting sensory stimuli based on live pulse data. Garmin wearables can already support this because they offer open Bluetooth Low Energy protocols. The Apple Watch, on the other hand, stores heart-rate data securely in HealthKit and makes it available through delayed write intervals. As a result, the current query mechanisms such as HKAnchoredObjectQuery or HKObserverQuery deliver updates with a latency of several seconds to minutes, which is too slow for the type of sub-second reaction required by driver-assistance or wellness systems.
I would like to propose that Apple consider creating a real-time HealthKit streaming entitlement for verified partners such as automotive manufacturers participating in the CarPlay ecosystem. This entitlement could be limited to specific biometric signals like heart rate, heart-rate variability and stress index, and should function only when the user explicitly opts in. The data could travel one way from the iPhone to the vehicle head unit during an active CarPlay session, remain local and encrypted, and never be stored in the cloud. A latency of around half a second would be ideal. Technically, this could follow an asynchronous delegate model similar to HKLiveWorkoutBuilder or a Combine publisher interface adapted for CarPlay Health sessions.
A capability like this would extend Apple’s health ecosystem beyond the wrist into the driving environment, allowing cars to respond in real time to the physical state of their drivers. It would strengthen Apple’s commitment to both privacy and safety, while supporting automotive partners that focus on human-centered design. Imagine a driver whose heart rate drops below a vigilance threshold: the Apple Watch detects it instantly, CarPlay transmits the signal securely to the ENERGIZING system, and the vehicle gently adjusts lighting and seat vibration to restore alertness.
This kind of integration fits perfectly with Apple’s long-term vision of “Health Everywhere” and would make a measurable contribution to road safety and driver well-being. I would be happy to provide a more detailed use-case document or to collaborate with the Health Technologies and Car Experience teams to outline how this integration could be implemented securely and efficiently.