IDC appeared to be overly optimistic on iPone world wide share for 2015. Isn't it really something like 10% now?One of the things that went terribly wrong with their prediction was Android vs Windows Phone distribution.
Twitter, why limit yourself with app list tracking? How about creating location graph, health graph, key logging graph, web site history graph and so on? I am pretty sure your users will happily share all their personal info with you.