For example, Skyward Mobile has an application that sells ring tones and wallpaper. While most mobile interfaces require a user to scroll through a list of textual descriptions, buying ring tones without hearing them or wallpaper without seeing it, Skyward Mobile's application plays previews of the ring tones and shows thumbnails of the wallpaper. The audio player is part of the application, and the user can buy ring tones and listen to them within the same interface, which isn't otherwise possible on some phones.

Although the server can only do so much--for example, some older phones don't play MP3 files--De Bonet says that a key part of the company's strategy is to reach a wider market by supporting phones being given away for free, as well as current high-end phones. He says that Skyward Mobile hopes to compete with larger companies by leveraging APX to build applications much more quickly than normal.

Nathan Eagle, an MIT research scientist who also develops mobile applications, says that there is a huge need in the developer community for tools that standardize application development across multiple devices. A successful tool of this type would give a developer access to hundreds of millions of phones and potential customers, Eagle says. Many companies are trying to solve the problem, he adds, including Adobe, whose Flash Lite platform is built into the hardware of many modern devices.

Tira Wireless's Lau says he expects that the proliferation of different devices will continue to be a problem, because handset manufacturers will continue to build products aimed at different segments of the market. While Lau believes that the type of approach Skyward Mobile uses can get rid of many problems associated with supporting different devices, he is concerned that building layers of abstraction onto devices may not allow applications to take full advantage of special functions that those devices may have. Tira Wireless specializes in individually converting and tailoring applications to different phones.

For now, consumers can purchase individual Skyward Mobile applications through Sprint and Cingular, as well as directly from the company through its website. De Bonet says that another version of APX is launching soon that will bring applications to Verizon customers as well. In the future, the company may take advantage of its system to sell bundles of applications or subscriptions--an obvious next step since all the company's applications install the same software on a handset. Although the company may someday allow other developers to build onto its platform, De Bonet says, it's keeping the technology for its own use for now.