Is there a way to scale font sizes?

Is there a way to make the font size variable?

The responsive design is awesome and I was thinking I could design the base template to work on different size tablet (5", 7", 10", etc.) but when I put it on the 10" tablet, the fonts are staying small while everything else scales correctly.

If not, is there another method to achieve this?

Thanks!

The apps themselves have a Scale setting on the Settings page. The default is 100%. You can increase that which will increase the size of everything, fonts included.