We just decided that we'd use DigitalOceans' servers with CentOS 7 as our cloud providers. For now we're using a single server for our database.

When the wristband detects a change in the values mesured, the data is sent over 3g to the server, as a JSON accumulate of data, and stored in the database. The server can then analyze the past data and detect any deviation. If the user wants to see it's history, he will be able to log in to the mobile app, or website and check graphs with his data history.

We are currently using Apache, MariaBD and PHP.