I developed Android app for q2a site. It is not free, currently using for personal sites. Here is apk and screenshot of app. You can download and see how it works.
Basically, i'm using google feedburner, which pulls questions from site rss. This way site will not have any load from app. Once user clicks on question then it will show in mobile view theme.
Download apk from below folder and try, let me know if you see any issues.
You can develop native or using phonegap. There is one free app developed by NoahY, it is integrated with site. check this link.