Here’s a great resource for working with maps on the iPhone: http://code.google.com/p/iphone-google-maps-component/
This code will allow you to add maps which are interactive including panning and zooming. Also, you can determine the location the user tapped on by pixel x/y or lat/long!
You can also add overlays for markers including customer markers. Based on tap events on markers, you can then display details, etc. Very cool stuff. Very useful.
A good use of this might be to provide geocoded information for sound data recorded on the iPhone. Check out http://cerkit.wordpress.com/2009/07/23/geosounds-com/
True. I also use it in NoonView to geocode pics uploaded to the NoonView server, Twitter and Facebook. http://www.noonview.com/