Since I'm a hopelessly addicted 360 image geek the first iPhone app I downloaded from the store was the PangeaVR 360 image viewer by Brian Greenstone of Pangea Software. The fascinating part of the app is how the image slowly floats from landscape to portrait mode as you move the phone around and how you move the pano around by dragging you finger on the face of the display.
Brian's design is simple and elegant! All you have do to allow a group of existing panos to be displayed on the iPhone is build a few lines of xml that has links to equirectangular JPGs for panoramas that you want to display.
Just for fun, I decided to make a iPhone version of the 360 tour of my Rental home. It took about 15 minutes and the result looks like this. iPhone users that have the free PangeaVR app and type in "http://lohrman.com/7318fairway.xml" into the "enter url" area of Pangea VR to display the tour.
Yea, I know, it's pretty geeky and not terribly practical. I wish Apple would just put flash on the iPhone so the same viewer that works in every other browser works on the iPhone but Steve is on a anti-Flash crusade so that will never happen.
June 14 Update: Brian reports that the PangeaVR app is the second most popular app on the iTunes app store in the photography category. In the first 4 days over 58,000 panoramas were viewed.