The square

Jack Dorsey, the co-inventor of Twitter, is promoting his latest
invention called the Square.
The square is a small plug-in attachment to your mobile phone that
allows you to receive credit card payments.

The idea originated from Dorsey's friend Jim McKelvey who was unable
to sell some glass work to a customer because he couldn't accept a
particular card being used.

Accepting credit card payments for something you're selling isn't
always easy, especially if you are mobile like a tradesman, delivery
service or a vendor at a trade show.

This latest invention uses a small scanner that plugs into the audio
input jack on a mobile device.

It reads information on a credit card when it is swiped. The
information is not stored on the device but is encrypted and sent over
secure channels to banks.

It basically makes any mobile phone a cash register for accepting card payments.

As a payer, you receive a receipt via email that can be instantly
accessed securely online. You can also use a text message to authorize
payment in real time.

Retailers can create a payer account for their customers which
accelerates the payment process.

For example, a cardholder can assign a photo to their card so their
photo will appear on the phone for visual identity confirmation.
Mobile devices with touch screens will also allow you to sign for
goods.

See Related Article On The Future Of Smart Phones
There are no contracts, monthly fees, or hidden costs to accept card
payments using Square and it is expected the plug-in attachment will
also be free of charge.
A penny from every transaction will also be given to a cause of your choice.

As with Twitter, it's anticipated that Dorsey will direct the company
based upon feedback from users.

Square Inc. has offices in San Francisco, Saint Louis and New York and
is currently beta testing the invention with retailers in the United
States.

Source: squareup.com