Hi,

For the blinds http://en.wikipedia.org/wiki/Laser_engraving laser engraved switch marks can be really useful. Rather than actuating a key press you may give a feedback through some digitized sound (Beep, ISD, RomanBlack, VS101, whatever) while the user scans the buttons. Hold (2secs... or whatever), or tap+hold, double tap, mixture of anything goes for registering keypress.