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Not sure why you'd exclude cloud in 2019 as that's the normal way to build such a solution. My Event Hub App in the store allows all sensor data to be uploaded in real time from as many watches/devices…
When your Garmin watch supports Bluetooth low energy broadcasting, you can also send sensor data to a PC through the Peloton open source bike computer, which is based on the Clue chip:
There is now a model available:
and a practical example:
ch.mathworks.com/.../collect-data-from-fitness-monitoring-devices.html
for BLE fitness monititoring devices in Matlab.