The Nike/Apple iPod trainer deal combines the weight of two of the world's biggest brands - and the devil has been in the detail.

Nike CEO Mark Parker and Apple CEO Steve Jobs explained some of the background to the deal at a press conference this week. Both partners confirmed plans to develop other solutions as part of their "ongoing partnership", BusinessWeek reports.

The two companies began work on the first solution all of 18 months ago, they revealed. Their teams "clicked".

Jobs explained: "Both companies are technology-driven companies. It's just that we work in completely different areas of technology. We are semiconductors and software, and Nike is anatomy and precision-molding and thin-film technologies. What's interesting is the people are very similar."

The first challenge was found in the sensor that is used in the shoe. At first it was too big for the shoe, and too small for Apple. Battery life and connectivity also posed problems, which is why the partners plumped for a proprietary development based on Bluetooth technology.

"The last thing you wanted was a wire going down your leg. It looks deceptively simple and that's how it should be. It took a while to get it right. But there is a lot of technology there," Jobs said.

At $29, the solution is eminently affordable for people who like to watch their exercise routine. It turned out that it's affordable by design: "We priced it so everyone can afford it because we want everyone to try it and experience how cool it is," Jobs said.