Using this app you can transmit integers, characters or strings using your voice. Click on the Bluetooth icon to connect with one of the paired devices. After a successful connection, you can click on the mic icon to speak the word or phrase. You can use the following program in Arduino to read the phrase received in the serial monitor.

//copy the program from here
void setup() {
Serial.begin(9600);
}

void loop() {
if(Serial.available()>0)
{ String data = Serial.readStringUntil('\n');
Serial.println(data);}
}