The Polar Sensor Logger app, developed by Jukka Happonen, Senior Specialist at Polar Electro Oy Research Center, logs polar sensor data to .txt files or sends them to an MQTT broker:
https://play.google.com/store/apps/details?id=com.j_ware.polarsensorlogger
This makes sensor data access easy. MQTT is supported by Matlab, Python, Influx dataDB, Grafana and other applications. There is an InfluxDB client for MATLAB and Python.
I miss MQTT support for all sport sensors, to put all sensor data into one influx database, MQTT should be standard, every athelete should be free to choose the application of this choice for his data analysis.
I miss an ANT+ sensor logger app next to the Polar Sensor Logger app.