I'm an experienced iOS developer and I have worked on a similar app, except it was an in-house app used for phone booth coin collectors. The app used an OpenStreetMap map.
I imagine you are making a sightseeing app that plays sounds or movies when you are close to a certain spot. Sounds and movies would be packed along with the app, so no connectivity is needed at runtime, or if you'd like it can stream them from a server; however, I would advise against this since it's hard to get good 3G coverage everywhere.
iPhone uses a combination of cellular and GPS, so it picks the most accurate available (obviously indoors GPS is not even functional), but it has very fast lock on the satellites once you are outside and it would work great for this kind of app.
I would provide you with the app along with a simple manual for compiling the app with different map, sites, and media files if you'd like to replicate the app for a different spot.