Build a POS receipt interceptor device

We need to develop a device to intercept receipt data sent from point-of-sales (POS) system to receipt printer. This device must be able to work with most of the common receipt printer brands out there, intercept data and convert into readable format. The device should be able to : 1. Intercepts receipts between POS terminal and printer 2. Read detail of the receipts : date, amount, merchant name 3. Communicate with our program which will return the appropriate message or image to be appended to the footer of the receipt 4. Send the print command to the printer with the receipt including the footer.