Hey there 
I recently bought an iPega PG-9025 Gamepad which i wanted to use with my iPhone 5s, especially with RetroArch.
This works fine, i can connect it via iCade Mode or Keyboard mode and map the needed Buttons to the Pad.
Unfortunately the “GamePad” Mode isn’t natively supported by the standart iOS Bluetooth which is required to use the Analog Sticks for gaming. Only iCade and Keyboard are natively supported.
But using a recent version of “Controllers for iOS” makes the Controller connectable to the iPhone via BTStack and the Analog Sticks can be used in iOS Games. I tested for example Sonic the Hedgehog 2 and it workls like a charm in Gamepad Mode.
My Question now is:
Since there are a some Emulators where Keyboard Button Mapping isn’t sufficient and an Analog Stick is required. Would it be possible to implement Controller Usage of the iPega in “Gamepad Mode” with Controllers for iOS in RetroArch to use the Analog Sticks for Example with mupen64?
When i try to use the iPega in Gamepad Mode with RetroArch after pairing with BTStack/Controllers for iOS, the Gamepad isn’t recognized and unusable. (what, in fact, was predictable)
Is it possible / Would it be much effort to implement this feature in RetroArch?
I think this would be a very reasonable extension for RetroArch because this Gamepad is very affordable (20 Dollars!) and is the perfect piece of Hardware to enjoy RetroArch when your are on your way. You can put your phone directly into your Controller an use it as a handheld, without carrying an PS3 Controller or anything else with you. If you could use the Analog Sticks now on iOS and could play for example Super mario 64 on your way, that would just be perfect.
Apart from this. Thank you for making retroarch on ios devices possible.