Tech Crunch reports:

As a general-purpose tablet, the iPad can be many things to many people: an ebook reader, a wireless TV, a touchscreen videogame console. But to store owners and business people it can also be a cash register, with the right app, of course. Jack Dorsey’s Square, which is already available for the iPhone, now has an iPad app as well (iTunes link).
Square comes with a peripheral credit card swiper that lets any store or business person take credit card (or cash) payments on iPhones, and now, iPads. It takes finger signatures on the touchscreen, generates email or SMS receipts, calculates sales tax, and comes with an online accounting dashboard to keep track of sales. (You can watch our video of how the iPhone app works).
The iPad version is going to be appealing to many merchants because of the bigger screen and because it just looks more professional—more like some of the custom point-of-sale tablets you already see at some retailers today. But an iPad is probably much cheaper than some of those custom hardware systems, and Square’s payments software on the backend will keep getting better. Square can add new features without swapping the hardware.
So while the iPad will mostly be a consumer device, it opens up some interesting new opportunities for businesses as well.

Very capable software and hardware. This is what they mean by the iPad bringing everything together!