I *love* my iPhone... and now the original Microsoft Labs codename for Deep Zoom - SeaDragon - has reappeared as the moniker for Microsoft's first iPhone application: SeaDragon Mobile!
There are some nice built-in collections to play with...
Notice the Virtual Earth Maps (Aerial, Hybrid, Roads)... SeaDragon even uses iPhone Location Services to tell me where I am! Virtual Earth on iPhone by stealth?!
It's more fun to view your own Deep Zoom images and Photosynths. Here is a collection of photos from Bhutan (created with DeepZoomPublisher) - press the [+] button in SeaDragon Mobile to Add Deep Zoom Content:
It's even easier to add a Photosynth collection (eg. CraigD)! Since there's a hook to Location Services, I wonder when I will able able to browse "Synths near me" (since Photosynth collections can be geocoded)...
You can also find or create RSS feeds of Deep Zoom images - example to come!
As Tim Heuer says, you can create your own Deep Zoom/SeaDragon images (for iPhone, and everything else) with Deep Zoom Composer too. Download SeaDragon Mobile here if you don't just search in the iPhone AppStore.