given that most TVs support this type of thing, I wonder if there's anything useful that could be built with the software.
Most TVs had an option where the teletext could have a transparent background and be overlaid on the picture.
You could use this to have different status things overlaid on the screen.
+ Because you can navigate to other pages [by manually typing the page no, or pressing one of the 4 colour buttons] - there is navigation.
I could imagine having an icon pop up, when your washing machine finishes, so you could empty it.
Or you could have pages so that you could see if you had new emails, that sort of thing.