I haven't unlocked all features yet, here's the apps you can use at the moment :
CALL, you can call your favorite NPCs to get mission hints. MESSAGE, you'll get information about current tasks from friends or guild admin. CONTACT, you can create favorite contacts list, up to six phone numbers. GUIDE, it'll show object & next area names on the map. ALARM, you can advance the time, instead of waiting in actual game time. CAMERA, you can take a screenshot, it's pretty useful for a bug report or tease me about the writing in this game. xD BOOST, you can skip barrier animation in the beginning of the battle, so that the battle command will appear faster.