allowing a URL to have a rendertype=tiny, or something
Um, I've used PerlMonks on tiny screens for years. That's why for years we've had the ability to insert /bare/ into any standard URL here (and why we don't use CSS for sizing and positioning of elements -- tables are much better at resizing than almost anything done in CSS, in my experience -- an experience that has repeatedly tried to prove otherwise but always failed).
There are several improvements that make a lot of sense for that "start", many of which I've surely talked about before. No, none of them are actually close to my top priority right now. I guess we'll see if anybody can effectively get that work done (one of my higher priorities was actually making it easier for others to effectively get changes applied to the site; sadly, it didn't turn out to be enough of a priority for some others enlisted to help on that -- maybe that will change at some point).
As for a mobile app, I'm certainly not stopping perl.j from writing one. Or was this a "please somebody else do that for me" request? :)