Yes, the Xiaomi notifies Whatsapp messages as well as mail calendars etc..
It didn't work for me at first and unfortunately it doesn't work anymore today.

What I can emphasise is the battery life, which is brilliant at over 2 weeks.
Unfortunately, I didn't take the accuracy as a priority, because I use the purchased band as a reference and improve with this information.

This works perfectly for me. However, the app must be open on the smartphone.

Ok your answer was informative for me! Many thanks and best regards