Square is a new startup that aims to let the iPhone and iPod touch (and eventually other mobile devices) to handle real-world credit card transactions via a small swipe-able accessory plug-in. Founded by the man created by Twitter, Jack Dorsey, TechCrunch scored the video demo above:

It’s a bit hard to see the iPhone’s screen due to the daylight, but you can easily see just how fast Square works for transactions. Simply put, it’s amazing.

Also note how I can sign with my finger on the iPod touch’s screen. And I can request to get a receipt via email, which I enter the first time, but the app will remember every time you come back and use the same credit card.

TechCrunch later posted a copy of what the receipt looks like. Apple Retail, as they point out, has been doing mobile transactions for a while, and are in the midst of switching from their old Windows CE boxes to iPod touch-based EasyPay solutions, but this solution is slick and looks to be well funded.

So, what do you think, is this the future of physical transactions, and do you want it now?