Preferably something that can be used to change it on the fly. Something like the Magnifier tweak that, AFAIK, only exists for the iPhone. Bonus points if you know of a free tweak, of course.
I'm not looking for system wide font size increase, two finger pinch to zoom, or the screen magnification under accessibility.
I want to be able to increase the font size, have text re-wrap appropriately, and I'd like to be able to do this from within Safari.