MacRumors reportedly got its hands on an Apple in-store training document, which indicated that the app needed to work with the sensor data is in the next version of the operating system, which went into beta in mid-November. The capability will initially roll out in the US.
It also says that it requires iPhone pairing for the actual data collection; that capability supposedly arrives with the next version of iOS, 12.1.1, Support requires an iPhone 5S or later.
According to MacRumors, the training doc says Apple Store salesfolk must warn potential buyers that the app is "not intended to be a diagnostic device or to replace traditional methods of diagnosis," and "should not be used to monitor or track disease state or change medication without first talking to a doctor."
Apple did not immediately respond to a request for comment.