Don't have anything too helpful, but if you haven't looked there before, I'd play around on http://hackaday.com/ maybe try to find where somebody did something with a HUD and contact them directly. They have some incredible things that people have made using the most random stuff you could...
This is a website I found a while back, its a great comparison of programming languages and their speed.
http://shootout.alioth.debian.org/fastest-programming-language.php
I think you're right in choosing C++ as a language, as you can see, C is minimally faster, but slightly more annoying to...