It should act exactly as if the data was being typed in. So you just need something that can read keystrokes. For instance, a quick hack workaround on an HTML form might be to have a field for card reader input - you just click inside the field, swipe the card, then a function that's triggered onkeyup from the field checks to see if you've hit the end character yet and then parses the input and splits it into the different fields. Or you could do that part with a button. Either way. I'd have to see an example of what it outputs to give exact code, but I could probably write you up something fairly quickly that integrates this using a web form and the Card Present Authorize.net API.
