We recently implemented a zork interface on top of Second Life so Visually impaired can access it using a screenreader. See http://textsl.org/
angrymilkman writes "Recently a number of interesting applications and tools have appeared that all focus on allowing visually impaired users to access the popular virtual world of Second Life. The University of Sienna developed a "virtual cane" allowing visually impaired users to get haptic feedback while exploring Second Life. The University of Nevada, implemented the interaction mechanism of the Zork text adventure game on top of Second Life in an application called TextSL which allows its users to explore Second Life using a screen reader and a command based mechanism. The guidedog project by the Virtual Ability Group offers a guide dog object -within Second Life- that provides a number of commands using synthetic speech that allow the user to navigate their avatar. Exploring how virtual worlds can be made accessible to visually impaired is an important problem as is evidenced by IBM Human Ability and Accessibility Center which recently developed a Virtual Worlds User Interface for the Blind which is a sophisticated interface that allows visually impaired to access Second Life from within a browser."
angrymilkman writes "Two interesting approaches where researchers modified the popular guitar hero game so it can be played by gamers with disabilities. Air Guitar hero (http://spectrum.ieee.org/nov08/6994) modifies the guitar hero controller so someone without limbs can play it just using electrodes attached to the user's residual arm. Blind Hero (http://kotaku.com/5092565/frets-on-fire-for-the-blind) is a mod for frets on fire that uses a haptic glove that can turn visual feedback into haptic feedback, allowing blind gamers to play Guitar Hero songs."
There are academics like me who just take existing games for their research. My students and I modify games so they become accessible to players with disabilities. See our one button version of halflife2 http://www.helpyouplay.com/gtf.html or our guitar hero for the blind http://www.helpyouplay.com/blind_hero.html