I've uploaded a new version (v1.09.3) for the Android version. It has a new Accessibility button in the preferences screen which opens up the accessibility menu. One of the options in there lets you increase the font size. It'll mess with the font size of buttons and such too though, so it may look wonky if you make it much bigger.
I haven't updated the demo yet, just the full version. I'll take a look at updating the demo next.