Was hoping to get real-time heart rates from SensorKit bit it appears the app must be part of an approved research project but I don't see heart rate specifically called out as being "sensitive" data.
Is a special entitlement required for getting heart rate data from SensorKit?
SensorKit does not provide real-time data. It all has a 24-hour "embargo", I suspect this is to allow the research participant the chance to revoke data sharing for 24 hours after any event. If you are looking for real-time heart rates, your best bet is HealthKit and HKAnchoredObjectQuery which can wake your app in the background as new data is written to HealthKit. There are, of course, some challenges/caveats - you must request and the user must grant read permissions to your app, and the phone must be unlocked for the updates to be readable for background updates.