Microsoft (MSFT) is working on an app store for its Windows Mobile phones — similar to rival Apple’s (AAPL) iPhone App Store — according to an alleged Microsoft job posting spotted by AppleInsider. The store, “Skymarket,” would work with phones running the new Windows Mobile 7, which is supposed to go on sale sometime

If true, this is a smart but expected move: Apple’s App Store is one of the highlights of the iPhone experience, and Google is readying a marketplace for its Android phones, too. If there really is a mainstream market for smartphone apps — the iPhone’s early success suggests there could be — any platform without an easy-to-use app store and installer will be at a disadvantage.

The challenge: Building something that’s as elegant as Apple’s iTunes software yet complex enough to deal with the Windows Mobile industry.

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