The mind-blowing thing, I see, is that—with that little doohickey—Square has single-handedly broken bistromathics[1]. And yes, you can take this comment as a joke, or you can take it seriously.
Do people really dream of such a thing? Some at PayPal thought bill-splitting would amount to something which was of course foolish.
The difficulty and hence lucrativeness of financial transactions depends on size, distance and familiarity. A large transaction across the world between two strangers is the riskiest/hardest/most expensive. A small transaction face-to-face amongst friends is the opposite.
Card Case doesn't happen to have an API, does it? ;)