A different approach was tried to keep the form factor of the mask attachment prototype small. This way it was split into two parts: One with Attitny piezo transducer CR2032 cell and 433Mhz Tx latched with Neodymium onto the mask;

the other part acted as a base station with 433MHz Rx connected to ESP32 which connects in Bluetooth HID to the Phone. Fairly usable prototype from the form factor point of view of the mask attachment.