You mean for a sound to play when game mode is entered or left, correct? Right now there should already be a spoken text when game mode is entered, but not when it is left. Just making sure we are talking about the same thing.
I like the idea, a sound would probably be better than text, because it is much quicker and less intrusive.
I'll look into the keyboard shortcut. I also want to make this a menu option - that way no one has to memorize all kinds of keyboard shortcuts by heart. NVDA already has a ton by itself.
Thanks for the link with the virtual revision add-on. I like the idea of opening a text window very much. I'll have to investigate a little though.
The accessibility plugin unfortunately doesn't actually wrap the Unity UI into native widgets. It quite literally re-implements the entire functionality of VoiceOver and TalkBack. It's a screen reader on its own. It was the only way to get it to work properly.
The only thing it needs is some way of generating speech, then it is almost platform independent. Almost anyway.
Currently it only works on iOS, Android and Windows (with either SAPI or NVDA). I plan on adding support for Mac and Linux too.
Web is a different story, because there are some WebGL specific issues that stop the plugin from working properly. Support for that is currently not on my roadmap