The app I think is only for apple products as I haven't seen it on the google play marketplace for andriod, though the official website say its coming soon for windows, android, ps mobile and vita.
As for the game - its massive in every sense, huge sprawling city and I haven't even seen half of it yet. Can't comment on missions as only done a couple but they seem very much what you would expect from the series.
Graphically its better in every way, rain showers leave the road wet, causing spray to rise from tires, reduced handling of cars. The cars look stunning, very much best seen so far, people seem much better animated and realistic.
If you didn't like any of the previous games i'd say that you won't enjoy this either, if you did like the previous, then this game keeps to the franchise well, and it seems better and improved in every way that i've seen so far. What I like about it is the sandbox style of a city being simulated so well, giving you the freedom to go and do what you want.
Although i've not worked out how to surface after you dive under the water and ive drowned a couple of times

Not had a go in a boat or any flying vehicles yet, but they have even put in sharks from what i've read and you can get yourself eaten by one if you so desire.
Considering the size and scale and whats in the game, its definately worth the money where other games that cost that price aren't, like the linear Call of Duty games etc. that you finish in a couple of hours. I can see me playing this for months before i've completed it, and even then there will be
something I can still try and achieve.