I think you’ll need to use the C API and ESP-IDF directly for that, see https://github.com/MrBuddyCasino/ESP32_MP3_Decoder.
That should run on the Pycom boards
Can you share what water flow meter you're planning to use?
Are you sure you want the WiPy to be a transmitter or a receiver?
@johand Good to hear that all is working now. :o)