UK-based RSLSteeper makes assistive technology for use in the classroom and at home, for all age groups and a wide variety of needs. It has recently released the "pererro," which provides switch access to iOS devices for those with fine- and gross-motor control issues.
At 30 × 28 × 9 mm, the pererro is roughly the size of Apple's iPad Camera Connection Kit and attaches to an iPad, iPhone or iPod touch via a 30-pin connection. It features a standard 3.5mm mono jack socket, so it can accomodate a variety of switches, including the popular Big Red Twist Switch. RSLSteeper also notes that the pererro also works with "almost any VoiceOver-enabled app."
Switch interfaces let users with motor impairments use devices like the iPad for communication, work and fun. I could not find pricing information on the pererro, but RSLSteeper asks interested parties to email or call with questions.