Its super simple and you dont need much to create one!
Step 1: Materials
It helps if you have an ipod or iphone to look at to see how everything works but it is not NEEDED.
To make drawing everything over and over a bit easier, I would suggest finding a picture on google of an iphone or an ipod touch and photoshopping the screen out of it so it gives you free space to draw!
Finaly you need to make enough photocopies for your animation, dont underestimate this, you will need alot.
Step 2: Drawing It In
This is very time consuming, you need to draw the same screen over and over (ie, lock screen, music, game)
Dont worry to much, if the drawing moves a little bit each time from where it's supposed to be, it gives it character.