Apple's iPhone has quickly become the world's most important mobile software platform. It's time for Microsoft, the world's biggest software company, to take it more seriously.

Specifically, Microsoft should start putting more resources -- not an insane amount, but more -- into developing software for the iPhone and iPod touch.

Related slideshow: 10 iPhone Apps Microsoft Must Make →

Why? Because while Microsoft is fumbling with its own mess of a mobile platform strategy -- Zune, Windows Mobile 6.5, Windows Mobile 7, "Pink," etc. -- Apple is the first to create a mobile software market that people actually use.

The company said this week that its 50 million iPhone and iPod touch devices have downloaded 2 billion applications in about 15 months. That's an average 40 applications per device -- a very high number relative to the rest of the mobile industry.

Meanwhile, of the 85,000 apps in the iPhone App Store, only two were made by Microsoft, the world's dominant software company. Neither has anything to do with any of Microsoft's core software lines.

They are:

  • Tag Reader, released in January, which lets you take photos of Microsoft Tag barcodes, which are designed to save you the trouble of typing a Web address into your phone. (These mobile barcodes -- not Microsoft's, but a more universal "QR" code system -- are popular in Japan, but not here.)
  • Seadragon Mobile, released last December, which lets you view high resolution photos.

These apps are fine experiments, but they're not creating any value for Microsoft on the iPhone. Instead, Microsoft should be working on iPhone apps like:

  • Office micro apps, so the millions of people who still read and create Word, Excel, and PowerPoint docs can do this from their iPhone. This should sync to Microsoft's new online Office. (And what about the Apple tablet? Won't that need Word, too?)
  • Zune music subscription player.
  • Bing. Why not? Google has a search app.
  • Games, like an iPhone version of Halo and throwback favorites like Minesweeper and SkiFree.
  • No doubt we've forgotten some. Let us know in comments which you'd like.

Microsoft could charge for many of these apps, and could also use some of them to extend its mobile ad platform.

Why might Microsoft be against doing this? Obviously, because it's probably focused on trying to build its own Windows Mobile platform, and doesn't want to help out its fast-growing archrival. (That hasn't prevented it from making Mac apps, however.)

But given Microsoft's horrendous history making mobile platforms, building apps for the iPhone isn't just a good idea, it could also be a smart hedge.

Related slideshow: 10 iPhone Apps Microsoft Must Make →