Hexy for the iPhone (apparently no relation to the Windows app of the same name) is a Hex game implementation by Sean Heber and Greg Nichols. It was released in November 2008, for purchase via the iPhone App Store.
Hexy supports board sizes of 11x11, 15x15 and 19x19. It allows a single player to compete against an AI (named "Buzzy"); or two humans can compete either on the same iPhone, or on two iPhones on the same local network.
There is no description of the strength of, or algorithms used by, the AI, although the game's credits screen thanks Jack van Rijswijck, Arthur Vause, Vadim Anshelevich and Cameron Browne for "inspiration".