Everybody knows that using a game controller makes playing on iPhones or iPads a whole lot more fun. If you know your 3D printing and electronics, you can always make your own. Adafruit has shared a guide that shows what it takes to make your own pinball controller for iPad using Teensy.
This controller gives you tactile feedback as you play the game. You are going to need arcade buttons with an enclosure, cables, and other simple components to complete this project. More info is available here.