Microsoft today is unveiling its new "OneApp" initiative, but contrary to the speculation that followed the recent discovery of a related trademark filing, it's not a combined Windows Mobile-Zune application platform. OneApp is a program to run mobile apps including Facebook, Twitter, Windows Live Messenger and others on feature phones, those low-end devices that come at little or no cost with wireless plans.

Except it's not something that people in the U.S. or other developed nations can expect to find anytime soon -- if ever -- at their local wireless stores. Targeted specifically at people in emerging countries, the initiative will be launched in the coming weeks through an initial partnership with Blue Label Telecoms in South Africa.

Microsoft says it will be striking similar deals to roll out OneApp through other wireless companies in developing markets around the world, such as India, China, Brazil and elsewhere.

The Redmond company's's Windows Mobile operating system for smartphones has been struggling against Apple and others in the market for mobile apps on higher-end devices. Microsoft says the separate OneApp initiative looks to take advantage of the widespread, continuing use of feature phones around the world. Tim McDonough, a Microsoft senior director, pointed out that feature phones will make up about 800 million of the 1.1 billion mobile phones expected to be sold in the next year.

"It's a massive category," he said.

The challenge for OneApp is that feature phones, by definition, are smaller, weaker and less consistent in design than smartphones are. The company says it has adjusted to those limitations by giving OneApp itself an extremely small footprint, about 150 KB.

Microsoft is also applying its "software plus services" approach that combines computing and storage on the device and in remote data centers -- shifting between the "cloud" and the phone depending on the amount of available memory and other resources on the device. The apps themselves are also small, averaging about 13 to 15 KB, and not exceeding 30 KB, McDonough said.

Despite those limitations, it's "a very good user experience," with graphics and not just text, he said.

There will also be specialized applications for local markets, such as a mobile wallet for making purchases or buying train tickets.

Pricing for usage of OneApp will be up to telecom operators and Microsoft's other local partners. In the case of Blue Label, for example, usage of the program will count against the prepaid data plans through which people use the company's wireless services.

McDonough declined to go into detail about how Microsoft plans to make money from the initiative in the long run.

"Our approach is to drive revenue for the ecosystem, and for us as part of that ecosystem. As time goes on, as we start rolling this out with more partners, we'll start sharing more of the business model," he said. Pressed for more details, he said there will be ads in the product over time, but he declined to be more specific about the company's plans.

Why not offer OneApp for feature phones in the U.S. or other developed nations? "When we look at how big the opportunity is in emerging markets, there's so much to do, to do that well, that that's our focus at the moment," McDonough said.