We are working on improving the mobile experience, especially with grid questions.
Soon we will also have a way to detect the width of the screen and optionally send respondents to different pages in the survey. Here is a work around for now:
1) Create a Free Format question named "screen".
2) Create a variable named "width" and make sure it is of type "hidden" and also set to "whole number".
3) Enter this HTML for the question:
<input name="screen_width" id="screen_width" type="hidden" value="">
You can then use Skip Logic to skip respondents with smaller screen widths to a different page in your survey. For example:
if screen_width < 800 go to Q5
Hope this helps.