This tutorial was more complicated. We made it much easier for You!
Just visit this page to learn how to connect Xiaomi Mi Band 1S and Xiaomi Mi Band 2 to the Apple Health app and transfer the results of continuous monitoring of Your heart rate to the Apple Health.
You would need Mi Heart Rate app to measure Your heart rate continuously on Mi Band 1S and Mi Band 2 see the data in Apple Health app.
I hope You would like it!