As mail-in payments drop by the millions and ACH cards account for the vast majority of bill paying in the United States, it's been just a matter of time before alternative financial services and mainstream banking began to share some products. This movement mirrors the growth of smartphones and tablets, allowing more people to use their mobile devices to pay bills anytime from anywhere. The latest player is the Bank of America, which is introducing a mobile payment plan open to any of its customers, but aimed at small businesses. Prepaid cards have been a financial boon to underbanked consumers in recent years, according to the Wharton School at the University of Pennsylvania. Prepaid options and ACH transactions have shown the more flexible and convenient a bill paying option is, the more popular it will become. Now, mobility has become all important as Bank of America's Mobile Pay on Demand suggests. However, while new to banks, such technology has been available for some time through PayPal, Groupon and other sites, according to PC Magazine. They use a similar card reader that plugs into the headphone jack of a smartphone or tablet and allows the consumer to swipe the payment card of their choice or key in the transaction.