If you sell small goods without a virtual store or even a brick and mortar store, that is, if you own the adult version of an ice-cream truck, peddling goods across large expanses of cityscape, Square’s latest credit card reader will be a God-send and it’s now shipping to customers.

Launched for iPhones and Android phones, it’s nothing but a plastic cube that latches on to your phone’s audio port and lets you swipe cards on the spot – a simple idea that could some become essential for some.

When a card is read, the data is converted into an audio signal and passed onto software in the phone, accepting most types of credit cards, from Visa to American Express.

The hardware and software are both free at this stage, Square charging only 2.75% and 15 cents for any transaction, independent of card used, and 3.5% and 15 cents as ‘card not present’ fees. It will even let you, as the vendor, check your transactions history against a map, in order to determine the spots where you get most customers.