scanForBluetoothDevices() can only be called once

[basvdijk]

You can only call await FTMS.scanForBluetoothDevices(); once:

    await FTMS.scanForBluetoothDevices();
    Stream<List<ScanResult>> scanResults = FTMS.scanResults;

    scanResults.listen((results) {
      developer.log('Scan results ${results.toString()}');

If there are no results and you call await FTMS.scanForBluetoothDevices(); again. XCode shows only one trigger of the Bluetooth scanning:

I think that the current default timeout of 4 seconds is too short.

FlutterBluePlus has a on option to scan continuously:

FlutterBluePlus.startScan(continuousUpdates: true);

Calling FlutterBluePlus.stopScan() will then stop the scanning.