Interesting article about how you can use viewport units (vw, vh et. al.) in CSS to change the font size dynamically with page width in a much smoother way than just going from 12px to 16px in one big jump at 800~ pixels.
An interesting technique, although what we really need is a way to figure out the physical size of the screen and the distance to the reader. For example, this technique would give the same font size for both an iPad and an iPad mini. Although I would suggest using a larger font on the iPad mini.