ESRI has been pushing their iPhone SDK quite a bit this year and everyone finally has access to it. I personally still think that web apps are the better choice on mobile devices, but for those who want to jump into Objective-C, check out James Richards blog post on developing with the new SDK.

All those folks below in that line waiting to get their iPhones must be totally ready to get your GIS app.

iPhone Line by JasonGardner, on Flickr
Creative Commons Attribution-Noncommercial-Share Alike 2.0 Generic License by JasonGardner