If you go with 1d barcodes instead of QRcodes (2d barcodes), no plug in need be used, not that they aren't worth considering for what they offer.
A 1d bar code can be printed simply by installing a font for that bar code. Many barcodes include a final "check digit" so properly producing a valid bar code may involve a calculation field that combines the item's ID with a calculated check digit. This depends on the specific bar code used and the formulas for calculating the needed check digit are easy to find in a web search. You can find custom functions for them that you can use as well.
The actual act of scanning a bar code is quite simple. Put the focus in the correct field and scan it. In principle, this is true for scanning from your iOS camera or using a USB connected bar code scanner attached to a computer. The scanned barcode can scan text right into a field where all you can treat this as you would any other text in a field.
In detail, Insert From Device is the script step that you would use to scan a bar code using the iOS device's camera. A blue tooth enabled scanner, on the other hand would scan data into the device just as though you typed data into a field from the virtual keyboard.
For QR codes, there are web services that you can use with a web viewer or Insert From URL to generate the needed code to print on a label for scanning.
Thanks Phil! That's exactly what I wanted to know.
How do the barcode fonts work when we might be printing from multiple machines? The little I read about them when I was doing my searching said that they can pose problems when using multiple machines on a network? Or maybe I misunderstood.
Barcodes could be generated via plugin on server as needed.
MBS Plugin does over 50 barcodes types including QRCode. (see Barcode)
For just the record ID a 1D barcode is enough.
But I would recommend to not use the RecordID. Generate some unique 12 digit random number (for EAN13 for example), add the checksum (e.g. via Barcode.EANChecksum) and make the barcode.
Than nobody can just modify barcode easily to find another valid one. With Record ID they could just count up.
Or even better use QRCode were you can use high error correction level and put more data inside, e.g. a GUID.
If you are using a font, that font has to be installed on the computer that is used to print the barcode. So if you don't install it on a machine and then print from it, you get plain text instead of a bar code.