This is pretty good for someone who can speak Cantonese but can't read/write it.
As an example, I speak Mandarin and can't read/write (much) Chinese characters as I spoke it at home while growing up in Australia. So, I can imagine there'd be quite a lot who are in a similar situation to me but with Cantonese who would benefit from this (not just as a learning tool).
I've been using the Zhongwen[0] browser extension to "read" websites that have Chinese characters for many years as hovering over Chinese characters will display a popup with the pronunciation ping yin. It may not be the speediest way of understanding a block of Chinese text.
I could imagine someone creating a browser extension that would replace the font used on the website(s) with the Cantonese Visual Font when the extension is enabled.
It's pretty simple to make.