There are several apps on the iPhone designed to accept credit card payments but, as far as I can tell, SquareUp has the best set of features. It doesn't require any contracts or monthly fees, and card payments can be accepted through a small device that plugs into the audio jack. Receipts can be sent via email or viewed online and text messages can be used to verify payments in real time.

There are even benefits to using the service for cardholders, much like the points you might accrue for making purchases. SquareUp lets business owners know that you are a repeat customer that may be entitled to a freebie—kind of like punch cards do now. They also donate one cent of each transaction to the charity of your choice.

SquareUP claims the service will roll out to everyone in 2010, which is good news for small businesses. No word yet on how much the swiping plug-in will cost, but you can bet that it will be a hell of a lot cheaper than the machines you currently have to contend with. [SquareUp via VentureBeat]

Dreamed up by Kim Young Suk, the One Card is almost too great to ever actually become reality. It would come with a media card slot to add credit card information, a knob to select which card you want the magnetic strip to mimic, and a display which would show either the selected card or corresponding receipts.

Only trouble would be that you're kinda screwed if you manage to demagnetize the card somehow. [Yanko Design]

The Price: $30

The Verdict: It does what it claims, which is hold two of your credit cards/ID cards simultaneously, but it's a pretty snug fit. The slight bending or bowing that your cards go through to fit into the slot shouldn't be enough to break it, but the two will scrape against each other because the space is so small. Which is good and bad.

On the one hand it's good, since it means your cards won't fly out of the slot when you're whipping out your phone. But it's also bad, since you'll have some slight difficulty in pushing out your cards. But it's not unusable, and it's not anything you can't overlook if your whole reason for getting this is that you don't want to carry a wallet on you.

Our only complaint would be that there's only room for two cards, and very little room for cash. Technically you're not supposed to even put cash into the slot, but if you fold up a couple bills, it'll still squeeze into the limited amount of space given.

Those of you who carry money clips will be familiar with only having your ID, one or two credit cards and some cash in your pocket. With this, you'll cut down the need to even have a money clip in addition to your phone, the convenience of which is probably worth $30 to you.

It does what it claims and holds two cards snugly

Slightly hard to remove the cards once they're inside

Not a lot of room for cash

The method can stop thieves in two ways. Those who copy down your credit card information will find that your account number and expiration date is not enough to place an order. And those who actually steal your physical card will find that they still don't know your pin.

While the cards house a 3-year battery, we're just hoping that they can stand up to a good pocket sweat. Because when we're roasting away in the summer sun, we need ice cream money to floweth from our plastic like a refreshing, icy deluge. [ITPro via gadgetell]