Following our report on the launch of Twitter CEO Jack Dorsey’s Square app and payment service for iPhone, Visa and DeviceFidelity have joined the iPhone payment market with a solution named In2Pay. This time, enabling iPhone uses to make contactless payments with their device rather than receive them.

Announced today, the In2Pay solution allows iPhone users to make “contactless transactions” by positioning their iPhone in front of a contactless payment terminal. In order to use the service, the iPhone must be housed within DeviceFidelity’s protective case, which uses microSD technology. The case is said to allow “mobile contactless capability” to the iPhone and is compatible with the 3G and 3GS models.

In a press release, Visa says: “By placing a removable In2Pay microSD into the protective case, iPhone users can take advantage of In2Pay’s secure contactless capabilities where contactless transactions are offered. They range from buying goods in retail stores and at unattended kiosks, to transit ticketing, and even securely accessing buildings and computers networks.”

Trials of the service are scheduled to start during the second quarter of this year.

The service builds on Visa’s payWave technology for contactless transactions and uses the DeviceFidelity In2Pay technology to make use of any mobile phones with a microSD memory slot. This suggests that the iPhone may not be the only device Visa is aiming In2Pay at. The iPhone, of course, does not currently support microSD and therefore needs a casing to house the microSD card.

“The more than 200,000 apps on the App Store are an integral part of iPhone users’ lives.” said Amitaabh Malhotra, COO, DeviceFidelity. “With our In2Pay solution, we want to give both iPhone users and app developers the power to do even more, by putting the convenience of interactive secure mobile transactions, right at their fingertips, anywhere they are.”

The In2Pay case is apparently designed to stay attached to the iPhone and offers a micro USB slot for charging and syncing their device.

It will be interesting to see how the service will be priced by Visa when it comes to roll out the service and, whether or not the DeviceFidelity case will be free or part of a subscription package. While the additional case could be seen as a benefit to some, many iPhone users dislike the idea of any housing that adds weight or thickness to the device and others preferring specific cases.