The video shows how the "Square" add-on clips into the 3.5mm jack on top of the iPhone and then processes the payment through an accompanying app.
The person taking a payment simply keys in the amount to be charged, and a note or photo of what for, scans the card and then passes the phone over to the customer to sign for the product.
Once authorised, a receipt can be emailed to the customer along with GPS co-ordinates of where the sale took place, in case of any foul play.
Rose does let us know he has backed this project with his own cash, but it does look promising - even in prototype form. Check out the video below and see what you think – here's hoping we see it on this side of the pond as well.