This is what I'm having trouble understanding about this thread. Barcode scanners read barcodes. Unless a lot of your inputs come to you with barcodes, the only way a barcode scanner would be useful would be if you used software to generate barcodes you could print and affix to any of your paper inputs. But why would you do that when you'd be limited in what kind of data a barcode could contain and how much? And for that matter, in the time it took you to create the barcode label you could have clarified and organized that input a dozen times over?
The same with NFC tags. Sounds nice but if I have a thought to capture it wouldn't be very practical to create an NFC tag when I could just write it down. I could maybe see the use for creating an NFC tag for groups of repeating tasks... except a lot of list managers allow you to save templates for reuse.
I'm not trying to rain on anyone's parade. I'm genuinely struggling to understand the potential appeal of this stuff for use with GTD.