One of the things I've enjoyed of late is a well made companion app.
I really enjoyed what Black Flag offered with it's app. the ability to play the fleet mini game, access to all the side information you gather in the game and a (somewhat) realtime map. The Division is apparently going to have a companion app that allows players to control drones.
I'd say that ESO certainly isn't designed around allowing something as complex as manning a drone, but things like a realtime map, access to the books your character has read, information on your characters stats and skills, access to things like an AH if one is implemented could make for a great companion to aid players in not having to open up their menus as often ingame.
I've seen a couple of MMO's toy around with the idea, but not with anything that would access the game proper. I'm wondering if there are security concerns for such an app.
Either way, make your vote and have your say! I look forward to reading both potential positives and negatives!