How to organize the transfer of data from wearable sensors via a smartphone to a server?

Question

Data transfer

Everyone, good!
There is a potential WRC topic - data transmission from a wearable sensor. There is a conditional wearable sensor of vital signs. I need to transfer data from the sensor to the smartphone, then from the smartphone to the server and from the server to the site. How can this chain be implemented?
I don’t ask you to do the project for me, I want to go through the whole stage myself. I need general knowledge, although the specifics will not hurt. Interested in what technologies can be used. Maybe someone knows interesting articles or has experience in this matter.
Thank you all for your attention!

Answer 1

In theory, nothing complicated, the most difficult thing in my opinion is writing an application for a phone that would route data)
And so the chain:
The sensor sends data to the smartphone via ble, the smartphone via mqtt data to the server, there this data is put into BD via mqttwarn

Answer 2

just like smartwatches do, for example, the doc can be read there:
https://docs.smartthings.com/en/latest/ref-docs/re...