I should add that the way SI did it in the old days was having a full-time data feed (via satellite) that they used to populate a database table used to display quotes with messages.
That's what I consider ideal, but via the internet. It doesn't have to be an ongoing data feed, although that'd be nice, and it doesn't need to be the whole market and every bit of data available. I'd prefer to limit it to only the tickers I ask for so I can save on bandwidth.
I used QCharts for ages. Might be time for me to take a closer look at QFeed and see if it can be used this way.