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Might I recommend that you make it a web app?

All of the facilities you have listed are available in Safari (client side storage, location data).

That is an option, but much more difficult if he is planning on selling his app.

Once it's developed and working, PhoneGap can turn it into a native app that can be sold on the App Store.

Also has the benefit that it can be potentially made cross-platform, so you're not as tied into just the iPhone.