First you have to be able to connect with your printer regardless of what you want to do. Easiest idea it to create a test layout and discover how to send that to your printer. Do a search in the Help for Specifying a Default Printer and Specifying a Printer.
After you know that you can print, then you proceed with how to print what you want to print.
Currently I have NOT found any label scanner that is zero contact just as you can wave your IOS device and take a picture. You have to tell it to do so, button and script.
Perhaps there is an add on scanner that once it is activated can do this but so far no app will that I know of.
Filemaker Pro can be made to auto-enter after a scan and I have done this by using the carriage return or tab that can be added to the scann data returned.
Before proceeding I would suggest you search the net for IOS scanners and visit the web sites to see if they will function as you wish since that is a a critical part of your plan.
Current I do not know, probably because I haven't done more than test numerous bar code scanning apps with Filemaker Go, whether or not you can get a reliable and comfortable auto-scan and script run.
This is a great need with Filemaker Go as you and others know. Filemaker INK needs to devote some resources to building in a bar code scanner in Filemaker go that requires a minimum of user action. I've posted a blog about this on my web site GoFM.biz you can search for bar code.
I am using CNS barcode as the scanner and I have linked it to FM Go using the fmp7 URL call back scheme. Works well to look up records in the fmp database after scanning a QR code. Its a one touch button in the FM Go Db.
I am using Printopia on a Mac with a Seiko Smart Label printer attached to print labels directly from the iPhone running FM Go. Would work with an iPad too.
Its pretty straightforward. Its essentially an inventory database so each item has a unique record. there is a label layout so each item has a label. the print script (attached to a single button) goes to the label record, does print setup, print without dialogs and has the label printer set as the printer; then returns to the inventory record. this is one touch label printing.
So this does require a computer on to run Printopia with the label printer attached to the computer. Not sure how this would work for you.
the problem i am having is that when i print the label from the iPhone and FM Go, the fonts are changed slightly (bigger). When i print directly from the database to the label printer it looks fine.
RE: the font switch problem:
I realized that label printing from FM Go will be limited to the fonts on the iPhone or iPad; a list is here: http://iosfonts.com/
It would be nice to have a condensed font to get more on the label but iOS does not support this and I have not jailbroken my iPhone to install new fonts.