Applications such as Square and GoPayment let you take payments with your phone.
A growing number of applications let you charge credit cards with your cell phone. Interchange fees vary, but they are typically lower if you use an attachment to swipe credit cards instead of keying in the information, because there's a lower risk of fraud.
Despite the name, you don't need a card swiper to use this iPhone app -- you can simply key in the information. The company that makes it, Simply Swipe It, offers its own merchant-account services, but you can use the application with any merchant account. It will soon offer an optional swiping device, which wraps around the phone and costs $150. COST: $15 to set up, $20 a month, and 15 cents a transaction plus interchange fees
VeriFone, one of the largest makers of point-of-sale terminals, developed this iPhone app. The company also offers a sleeve for swiping credit cards; it retails for $149. COST: $49 to set up, $15 a month, and 17 cents per transaction plus interchange fees
Intuit's app works with a wide variety of phones and can also be used through a mobile Web browser. Purchases sync with QuickBooks accounting software. You can get an optional Bluetooth card reader ($145) or card reader and receipt printer combo ($219). COST: 30 cents per transaction plus interchange fees. You pay a minimum of $13 a month.
This app and card reader from Twitter co-founder Jack Dorsey works on iPhones and Android phones. COST: Dorsey says the device, which is still in beta testing, will be free. Users will pay a flat swipe fee that has yet to be announced.