Odyssey Space Research has sent two iPhone 4's to the International Space Station after modifying them to meet NASA flight certification standards, the company says.

The iPhone 4 was selected for its mix of features, said Brian Rishikof, CEO of the Houston firm.

"It had a three-axis gyro, and accelerometer, a high resolution camera and screen, and the means to manipulate the image. We had done some projects in the past that used all those features, but of course it was big, dedicated equipment and suddenly here it is in this small little package," said Rishikof.

The smartphones use the same software as their Earth counterparts and Odyssey used standard tools to develop a new app called SpaceLab for iOS, which is also available for customers to download to their own devices.

The devices are part of an study called NanoRacks Smartphone, which looks at how the phones will operate in space. The hope is to use the compact hardware in future research studies and to augment crew performance and productivity. Four experiments are being run on the smartphones via SpaceLab for iOS.

Another goal in sending the phones to the space station is to engage the public. The SpaceLab for iOS app for users on the ground is identical to the software that was downloaded onto the space devices prior to launch.

According to Rishikof, there is a setting in the application that indicates if the equipment is in microgravity or not. The software operates differently to accommodate the presence of gravity.

"There are 200 million devices that run the operating system and could potentially run the application," said Rishikof.

"Which means there are 200 million users out there that could get a sense of what it does; a sense of what an experiment in space might look like; a sense of participation."