You need the app. Without it you can't register the device and pair. Borrow an android device to register P3 and then fly without app until iOS app is released.
I am giving this advice based on what I had to do in order to fly mine.
Yes. I needed to in order to get the damn thing flying.
First thing it asks you is to put your name to start the 1 year warranty. Then it asks you to login to your DJI account. Then it asks you if you want to fly in beginner mode... goes through tutorial... ready to fly. You can now take off with or without the app.