Count Ingenico SA among those that believe that mobile devices and payments will converge.

Christophe Dolique, Ingenico's executive vice president of transactions services and global marketing, said the French terminal maker invested $6.5 million last month in Roam Data Inc., a mobile payment-application company in Boston, as a way for Ingenico to "address the mobile merchants market with a comprehensive set of security payment" offerings for any mobile device.

Dolique estimated there are 100 million mobile merchants globally, including home-based sales, plumbers, direct sellers and small fleet delivery drivers.

Roam Data received $8.5 million overall in its latest round of funding, said Will Graylin, the chief executive of the company. Other investors include George Wallner, a founder and former CEO of Hypercom Corp.

The Roam Data product enables payment and business software to be written for mobile devices without having to write a specific version for each version of a device's operating system. Applications made by other companies for Apple Inc.'s iPhone and Research in Motion Ltd.'s BlackBerry devices are problematic because they are made only for those devices, Graylin said.