There are also these mobile-web alternatives: http://hnmob.org/ http://ihackernews.com/
You can also look at the source for HN, http://arclanguage.com/ And some other places on github likely; it's not easy to get that code running. Also, I'm not sure it's easy to make the updates. Plus, Nick is very busy.
hnmob.org only formats front page while the comments pages (which can be the hardest to read) still link to HN.
ihackernews.com does not have a search function and login seems to be not working, also check author's own explanation at http://ihackernews.com/login
In my opinion there simply doesn't exist a web or native app which works 100% and never needs you to flip back and forth from news.combinator.com
As @kowdermeister said, it won't require much, just a couple of media queries. I'm not a fan too of over complicated things and I like HN raw, essential style. That sort of raw, minimal rule could also be used for a request from a smaller width device.
Still a little sloppy, I'm only hacking this code when watching TNG re-runs (so every day ;p )