Cash is so old school. And so is that flip phone you have. So why not upgrade to an iPhone with Square’s card reader and solve both your problems? Square, Inc, a company founded by a cofounder of Twitter, is the first company created to bring credit card scanning to the masses. With a small, free, and little device, anybody who owns an iPhone, iPod touch or iPad can turn it into a mobile cash register. It’s quite amazing.

Jack Dorsey, the inventor and chairman of Twitter, has just announced his new startup: Square. Square is aiming to be the ultimate pay-on-the-go credit card system for the iPhone, requiring only a small credit card slider that can be plugged into any device with an audio input jack. Basically, using the powerful abilities of the iPhone SDK and ability to interact with third party hardware, SquareUp will allow iPhone users to make their phone the ultimate payment portal.

Apple could already be testing next generation iPhones equipped with RFID (radio frequency identification) capabilities if a less than rock solid rumor is to be trusted (as if rumors could be solid in the first place). What exactly would you do with RFID in your iPhone? A host of things actually, but the most useful for regular users would likely be how it could simplify device discovery and syncing.