Square is a new company founded by Jack Dorsey. Their product is a small card reader that mounts onto your iPhones headphone jack and together with the accompanying app it let's you charge credit cards with your mobile handset.
Along with services like Zopa, Obopay, M-Pesa and Mint Square is a nice addition to the type of services we need to kick some new life into the stuffy world of banking.
They've done a nice video to show off the product, please take a look.