Found in various early vintage MacBooks.

We've got one hundred of these nifty little Square card readers available now for local pickup here in Seattle. (Beats waiting a few weeks for them to ship you one after you create an account using their free app.)

What is it? Square is a convenient way for small businesses to accept card payments using an Apple iOS (iPhone, iPod touch, or iPad) or Google Android device.

The Mac App Store looks like it will simplify getting and maintaining software (just as we have seen it do in the iOS ecosystem).
I've downloaded and recommend, if you can use them:

• Twitter (free) 
• Courier (reduced to $4.99 from $19.99)

Sent from my iPhone