I have the Index BPM and I have turned on syncing to Apple Health from within Garmin Connect.. I've found that within a given day, the Index BPM will always overwrite the previous measurement from that day -- so Apple Health will only retain ONE blood pressure measurement from the Index. So, if you take measurements in morning and evening - Apple Health will only keep the evening measurement. By contrast, my Omron will sync every measurement through the day to Apple Health. I contacted support on this, but the response was this was an Apple Health problem -- which I doubt because the Omron retains every measurement, and my previous Balance Health monitor also retained all measurements in Apple Health.
YES -- all of the measurements are available in Garmin Connect -- but it is much easier to flash the Apple Health screen to my doctor to quickly show my history of my own measurements. Below is screenshot.. I had multiple measurements from Index on 6/15 and 6/14 -- but as you see, it only retains the last one. Anyone else have this issue or a solution?