Since I started this wiki, I am seeing more information becoming available for using the iPad for students with significant disabilities. Here are some links to articles that might give you some ideas.

iPad Project Gives Voice to Students with Severe Disabilities (Anoka, MN) December, 2012.

Use of the iPad for Students with Significant Intellectual Disabilities (Virginia) September, 2011.

iPhone/iPad Accessibility (James Nuttall's blog) Jim is legally blind and has dyslexia. He lists 50 accessibility features available to him on his phone. December, 2012.

Video of iPad use by student with Down Syndrome.

Video of iPad use by student with spinal muscular atrophy (New York Times video), October 2010.

Video of how iPods were implemented in classroom, using signed videos 2009.

Video of iPads for Special Needs Commercial by Luis Perez., February 2011.

Video: Hands On Music: An iPad for Students with Disabilities

News broadcast from Wall Street Journal (first 5 min) Digits Live Show: iPad Gives Special Needs Kids a Boost, October, 2010.

, Using the iPad and a Sequence of Apps for Young Children with Multiple Disabilities, Fall, 2012, California Deaf-Blind Services

Garden of Eagan, blog covering apps used with children with Down syndrome, written by parents of three children with DS. Identifies pros and cons of many apps they tried, January, 2011.