Thermometers from Ink-Bird (e.g. [login to view URL]) send values via bluetooth. The app should connect to a device and read values once per second to store them on the phone as CSV file. There's plenty of examples on Github containing info about how to connect & receive data. Please let me know what four plus three is to make sure you have read this description. No fancy stuff needed: just a small app, that connects to the next available thermometer. Start & stop logging by pressing a button in the app. Make logfiles available for sharing and removing.
Please find an idea of what the app should look like attached.
Here's code examples and details on how to communicate with devices: [login to view URL]