Yes, Riptide GP2 has MFi controller support!
Riptide GP2 on iOS does support controllers and is compatible with the MFI standard.
The premier console-quality water-racing game on mobile kicks everything into overdrive, with intense online multi-player races, upgradeable hydro jets and riders, improved graphics, an all-new career mode, and a whole new stunt system with dozens of new tricks! Featuring rocket-powered hydro jets racing around futuristic tracks across a dynamic and interactive water surface, Riptide GP2 delivers a fast, fun, and visually stunning racing experience.
ALL NEW CAREER MODE Play through Race, Hot Lap, Elimination, and Freestyle events to earn XP and cash that can be used to upgrade your hydro jet, unlock new stunts, and increase your rider's performance.
ALL NEW WATERCRAFT Collect 9 powerful new hydro jets, and upgrade their performance and colors to gain an edge on your competition.
ALL NEW STUNT SYSTEM Unlock and master 25 outrageous new stunts.
Riptide GP2 supports MFi controllers.