The release this weekend of Microsoft's first iPhone application, Seadragon Mobile, got us thinking about which Microsoft programs might be the next candidates for adaptation to Apple's popular mobile device.

Of course, Office programs such as Word, Excel and PowerPoint would seem like logical choices, and Fortune reported earlier this year that Microsoft's Mac Business Unit was weighing its iPhone options beyond the current trick for displaying PowerPoint slides.

Hey, wait a second. What about a Zune app for the iPhone?

Sure, it sounds crazy, at first. But offering elements of Microsoft's competing music service on the iPhone might actually be a shrewd business move for the company to make. Are we nuts? As a reality check, we've asked the Zune team if it's pursuing or contemplating such a plan, and we'll let you know if we get a response.

In the meantime, here's our wild theory.

Microsoft CEO Steve Ballmer has already made it clear that the company is planning to offer Zune software on phones running the Windows Mobile operating system. Of course, the iPhone isn't a Windows Mobile device, but Ballmer's comment at least shows that the company is generally open to the idea of extending the Zune experience to non-Zune mobile devices.

Zune remains a huge underdog to Apple's iPod and, by extension, the iPhone, which incorporates iPod functions. So Microsoft is in a position to make bold moves. Seriously, at this point, what does it have to lose?

But the clincher is the Zune Pass music subscription service, which lets people pay a flat monthly fee for blanket access rather than buying individual tracks. It's the Zune's biggest point of competitive differentiation against the iPod. Apple doesn't offer subscriptions.

So why not offer a limited Zune Pass as an app for the iPhone and iPod touch? It would be like advertising for the Zune -- giving iPhone and iPod users a taste of what the Zune is about. Then, for the full experience, they would need to switch to a Zune device. It's a modern twist on Microsoft's classic strategy of "embracing" and "extending" rival technologies.

Of course, the iPod and iPhone will no doubt prove much harder to "extinguish" than past Microsoft competitors.

And yes, there would be all sorts of complications, such as licensing terms with the big music labels. (Most common on the iPhone now are Internet radio apps that stream songs but limit a user's control over which song is playing at any given moment.) Not to mention the fact that Apple would need to approve any Zune application for inclusion in the App Store.

But that's our crazy idea. Let us know what you think. And apart from all of this Zune wackiness, feel free to comment below on which Microsoft programs you would most like to see offered as iPhone apps.