I'll definitely look into this, but it does appear to be something a bit more application specific.
My initial thoughts would be to use an android device and a javascript library. Since iOS does not allow for direct access to the camera with getUserMedia, you would have different functionality between platforms.
Were you thinking of a USB Barcode scanner or something similar? I wonder if they make WiFi barcode scanners that can make an post to a web API.
One thought would be making a CLI utility so that you can generate the files without having to add/remove the gem. This way, it would be a globally accessible thing that could easily be used on other projects.
You may not need foreman with puma-dev since it will automatically start up your Rails app on the first request.
Puma-dev wouldn't automatically start those services. It will just start the Rails app.
Is the JS in your view or in the assets?