Hello,
I have two iPhone apps - one provides maps, online and off. The other includes the map application, and also provides a GPS recorder.
I would like to sell the Offline Maps app, and then have an option within the app to upload to the full application. How would I go about doing this?
In my code, I build two different targets against the same codebase to produce these two apps.
Unless something has changed, you are not allowed to upsell to another version. Apple will deny your app.
Erica Sadun has talked about it: App Store Lessons
Clarification: I grok that as: You can make two versions, but they must stand alone and can't talk about each other. Sorry, I realized it might not be clear after I answered. You can make them, but they can't be aware of each other.
Right; you can now upgrade within an app though. I've not done it yet. My understanding is pretty limited of that, though for one thing I remember reading that you have to create a specific authorization code, not the wild-card *.com.mydomain type, when you create & submit the app if you are going to do in-app sales.
You need to look at the 'StoreKit' framework. This new framework, introduced in iPhone OS 3.0, allows the purchase of new content, be it game levels, electronic assets and yes, new features right in the app, piggy-backing on the iTunes payment infrastructure.
Basically, you supply the content through a special iTunes Connect sub-system and the API gives you all the hooks you need to determine if a user paid successfully, etc...
http://developer.apple.com/iPhone/library/navigation/Frameworks/CoreServices/StoreKit/index.html
I should note that you'd likely have to change the way your app is built / currently works but if you're willing to adapt to StoreKit, you should be able to build what you're describing as far as an end result.