I have a problem too. I've reached the reading glasses stage and have problems with small text. I was actively looking for a solution recently, something like the Readability or Clearly extensions which work well in Chrome on the laptop but I failed to find anything like that for the iPhone. I was considering trying to make my own app to do it with the idea of using Phonegap/Javascript to read the html for a site and then process it in a Clearly type manner. I'm not quite sure if that would work? I think cross site ajax requests don't work in most browsers (http://stackoverflow.com/questions/15005500/loading-cross-do...) but I vaguely recall they did work when I tried them from Phonegap on the phone.
Mobile Safari has "reader view" build in for most sites, but it doesn't work on every site. It works on most blogs and news sites though. You can find the button left from the URL.
Desktop Safari processes the page to try and identify if there is a block of text that might look like prose. If it finds it, you get the button. If it can't, you don't.
I do most of my iPad web reading through an RSS reader like Mr. Reader because of a similar issue. Mr. Reader lets you choose between 5 built-in (including normal web view) page views as well as allowing unlimited user created/added bookmarklets, javascripts & URL Schemes. An iOS add-on that would flip any Safari page to a customizable Reader/Readability/Clearly view would be nice, though.
