There are four nexus 7 tablets, and a movie. The movie is divided to four regions perviously. Now there is a need for a app to start the playback of these 4 parts of the movie at the same time and keep them in sync so that the 4 tablets show the entire movie as a single screen.
The movie parts are stored locally in each tablet.
Tablets are connected to same WiFi network, so they can use this property to sync with eachother.