I need to start an HKObserverQuery on heart rate data when the phone is locked, and then read this data when notified still with the phone is locked. The trigger to start the HKObserverQuery would be an apple watch message which will wake-up the iPhone counterpart app on the lock phone.
Is it possible?
HealthKit data is not available while the device is locked. You can start your HKObserverQuery while locked, but you will not receive callbacks and, if you are using background delivery, your app will not be launched for new data until the device unlocks and the Health database is available.