i>clicker has created a new student response mechanism that runs through a Web browser. web>clicker allows students with any device that runs a standard Web browser to vote using laptops, PDAs, and cell phones. To help with accessibility, web>clicker provides screen reader applications and the ability for the instructor to pre-load questions, thus helping those with visual or auditory impairments.
http://thejournal.com/articles/2010/03/22/iclicker-intros-web-based-clicker.aspx