The world's largest software company today released their first iPhone app dubbed "SeaDragon Mobile".  Seadragon is an application designed to browse high quality imagery and is in the same realm as Microsoft's Photosynth technology.  Get it here (iTunes link).  You can pinch and zoom around gigapixel images surprisingly fast according to Microsoft:

Seadragon is designed to provide next-generation visual experiences, regardless of the size of the screen, size of the file or speed of your network.  It's already available on a number of platforms, including Microsoft Surface, and in Photosynth and Silverlight. Now we're bringing that same graphical smoothness right to the iPhone in your pocket.

Create your own content with the Deep Zoom Composer or PhotoZoom and view it on your phone.  Or just look at our sample content. You can also browse Photosynth collections (yours or anybody else's) with just a flick and a pinch.

We will continue to experiment with bringing Seadragon to other platforms as we move forward, exploring different ways to use this functionality to improve the way users explore the digital world. 

Interestingly, Microsoft expects to release more apps in the near future according to their website.

As a Microsoft tech notes below, the browse Photosynth is broken - which is most of the app. So there isn't much to see just yet.  You can still find friends by name and add synths (just not view?!).