Been thinking about untapped markets that video games haven't entered yet and there are several. My final year project doesn't require players to be able to see. Amputees that only have one hand or people with other hand disabilities, or even people that want to multitask in a way I would rather not think of will actively seek games that they can play one-handed.
There is a population of people out there that suffer from a type of epilepsy that was probably discovered when they where playing a video game as a child and can't allow themselves to watch any flashing lights or repeated patterns. For epileptics the conditions for them to have a fit are very specific and there is software out there which will monitor what is being displayed on a screen and produce a graph of probability of a fit occurring based on what is displayed. The worst offending titles are older, so called 8bit titles, so many newer games would probably pass such a test without incident.
I really do think that a sticker on the back of a gamebox describing the control interface of the game or wither or not the game is safe of epileptics would benefit the disability community and grow the gaming population a little.