Scanning barcodes into third party apps
It's easy to achieve a similar workflow with an off-the-shelf barcode scanner app such as ZXing's Barcode Scanner. After scanning a barcode in that app, you can press a button to copy the scanned text to the clipboard. After switching to your other app, you simply long-tap the text field to paste the text into it. It's a few more screen taps than you're imagining, but that's the easiest way.

There's also a keyboard app that has a button to scan a barcode and enter the scanned text as if typed in. It's non-free, and requires replacing your soft keyboard, but Barcodescanner Keyboard lets you shorten the workflow by a few taps.

Any better solution would require some kind of bespoke development, whether that's modifying the target app or making a custom ROM.