There's quite a few apps for reading SMS messages in big font, but I can't find any way to write a SMS using a font in 30+ points of size. Any help would be greatly appreciated, I couldn't find anything suitable using Google nor Android Market.
You can't determine the font size the other person sees messages in. Size and characters are completely different things. You see an "A" and your phone has been told to display it large. You can't send a "large A", just an A. SMS isn't HTML.
I feel your pain. I consider reading glasses to be a necessary peripheral for a phone. But I don't know of any way to increase the font size without replacing the phone (say a Note, which has a large screen).
OK, GO SMS Pro allows to increase the font size in the input field, but only a bit, and no ability to change text/bg color, which is shame compared to other areas of customization. Other tips still appreciated ...