I am building an app that will run on a user's iPhone and iPad. People will enter information on either device. I am looking for methods in which the data can be synchronized between the devices.
Would I have to force people into something like iCloud or Dropbox?
I think It would be a good idea to consider using iCloud as iOS 5 will soon make this the accepted standard and people will expect it.
If you don't want any sort of server-side solution (i.e. iCloud or something you write yourself) then have you thought of bluetooth / wifi - assuming the users will have their devices near to each other then you could sync directly from device to device.
However, I would probably have some sort of server that did the sync and stored the data - you could make this free for a certain amount of data and then charge for anything more than that - hopefully that would recoup the cost of running the server.
来源：https://stackoverflow.com/questions/7380264/xcode-share-data-between-ios-devices