All of this can easily be done with some programming. I've done some work writing inventory systems. Here are the quick plans. You could probably do all of this in excel and a pos scanner.
1. Create a form with an incoming and outgoing text box
2. When you put beer into the fridge, you put the cursor into the incoming text field and scan the label. The scanner will convert the barcode to a unique number (upc).
3. Your query your database\spreadsheet for the barcode number
3a. Barcode found- You enter how many beers are going in
3b. A form pops up for you to create a "beer profile" (name, company, product, abv, etc..). You will enter the details so you do not need to deal with the UPC database. You enter the number of beers going in
4. A "lot" is created with the inventory amount
5. When a beer is removed, you put the cursor into the outgoing text box and scan
6. You enter the number being removed and this number is subtracted from the "lot" quantity based on the barcode number you entered earlier
7. A report will list the lots with quantities and other info
8. Homebrew can be inventoried by printing "3of9" barcodes on suitable media (round cap stickers?)