While there are a few minor issues[1,2] it works with iOS 9.
 The firmware download manager is broken.
 The wifi signal gauge shows always low signal, this does not effect the range.
Make sure that you activate the flight mode first in your settings app (the one with the gear). 3G network should be off, then activate wifi and connect to the AR.Drone wifi network. Now open the app.
Basically every MFI gamepad with extended layout (2 additional analog sticks) should work. Development was done with the Moga Ace Power and the Stratus Steel.
They suddenly stopped making the gamepad around September 2013. If you still can find one, don’t pay more than 30 dollar.
You will be in good hands in the english board for Parrot drones like the AR.Drone: www.drone-forum.com/forum/
Currently the app is only available on iOS. An Android app is planned, but we can't give an ETA at this time.