When trying to use barcode scanner in bad lighting conditions, it would be very beneficial if possible to light the LED/Flash that comes with the phone/tablet
I have found out that the ZXing library that is used by the ngCordova BarcodeScanner automatically supports this feature (although it is not yet documented). The source code states that if you click the volume up button then the LED/Flash if present will be lit up. Clicking the volume down button will turn off the LED/Flash.
Although I can not be 100% certain, but given the life of ZXing library for CaptureActivity I think that any barcodescanner using it will be able to use this functionality assuming a flash is present.
Hope this helps someone.