Apple’s App Store hit 1 billion application downloads today, which is quite the accomplishment given that the mobile-phone store has only been in existence for nine months. Given the iPhone’s early successes, it’s no wonder that there’s plenty of companies—from carriers to retailers—that are eager to follow their lead.

SEE ALSO: Wireless Carriers Are Increasingly Interested In An App Store-Like Business, GetJar Says

However, they are finding that it is a ton of work—everything from aggregating the content to figuring out how to charge for the applications can be a potential roadblock. That’s where a number of companies have carved out a niche for themselves. Today, Kansas City, Mo.-based Handmark unveiled its Mobile Store Platform, which helps others launch an app store using Handmark’s library of content and customizable user interface (Release.). Also offering similar services are Handango and GetJar.

Handmark said that the platform is ready to launch on some Windows Mobile devices and will soon announce its first customer. It will also be available for other smartphone platforms soon. In March, Handango announced its “App Store Accelerator” and says it is currently being used by BestBuy and Verizon Wireless (NYSE: VZ) (Release.). And, GetJar told us last year that at the time it is working with more than 10 carriers worldwide. The move to outsource at least some or all of the functions within an app store is smart. For many of these companies it’s not their core business, and developers will have to pick which application stores they can afford to support. A wholesale model will streamline the business for both app-sellers and app stores.