For a simple example, if an app can display photos and someone takes a new photo, then the other people who have the same app, in the same group(if its possible to group this way) that has been created beforehand, will get the update of the new photo - (the list of photos would change and the app would handle that accordingly) (and updated via a push notification or some other automatic 'update'). This would also be useful for also editing a photo and updating that and for others to get that update.
I am wondering what are the options available (iOS 8+ only solution for now) to:
Have someone download an app and "invite" others who have also downloaded the app to be a part of their group - so that they have receive any additions or updates to the app in the way that i have described. I would really really not want to have to know someone else's e-mail address for this. Looking for another option.
Sharing this data between group members (and this solution might depend on #1, I am not sure).
I have read on here solutions like NSUserDefaults or key-chain grouping but since we are talking images here and depending on #1 there might be other better solutions.