Clouds a problematic because of privacy reasons. But a computer based open source data analysis tool would be helpful, based on InfluxDB, Grafana, stored locally on a mini PC.

After I reviewed for a longer period of time, I came to the conclusion, that a Rasperri PI with Ubuntu is an interesting device because of power consumption. Many applications run on it, for instance ANT+ sticks for sports sensors, brainwaves can be stored locally on a Rasperri PI:

https://blog.adafruit.com/2018/05/28/recording-brainwaves-with-a-raspberry-pi/

There are complicated instructions on the web for Influx DB, Grafana, and Rasperri PI:

Alternatively to Node-Red, the Home Assistant software can be used to stream sensor data over MQTT to InfuxDB and Grafana. There are plugins available for InfluxDB and Grafana, and there is also a version for the Rasperri PI.