Here is an interesting free download to adapt two Wii games for use with children who are visually impaired - VI Fit.
This adapts Wii Tennis and Bowling. The VI Fit download provides audio and vibrotactile cues to direct the players where to hit and direct the balls.
VI Tennis was tested on a group of 13 children who were blind and resulted in increased active energy expenditure. VI Bowling was tested on 6 adults who also increased active energy expenditure during the game.
Go to www.vifit.org to get the download and directions.
If you need off the shelf adaptations for the Wii check out this website for available products - http://www.broadenedhorizons.com/wiimote.htm