I think this app will be a huge improvement to playing Grepolis from your phone. Besides reading your messages, and receiving a notification that you're under attack (Also when it's from an Island Quest...), I see little use for the current Grepolis app, because it's so time consuming, and some of the prime features - such as alliance overview, a map, world wonders (I noticed how important this is just a few weeks ago when WW Era started on Alpha) and for premium users, the captain (simplified farming villages) - are not available.
If all of the new Grepolis App is as good as the map feature of the video Daedalus posted, I'm sure there will be a major increase in the use of the Grepolis App by many Away-from-Keyboard players.