divVerent created a radar for Nexuiz using CSQC which I believe is actually more complicated than Halo's radar.
This isn't the most flattering picture of the radar: http://pics.nexuizninjaz.com/viewer.php ... pxzbgl.jpg
but it shows it none-the-less.
He wrote something to generate the map images as well \m/(-.-)\m/
He's stopped making the daily / weekly builds, so the best way to test this out is to build from SVN or join one of the SVN servers with the compat pack.
The Nexuiz Ninjaz, de. greens and Over the Lazy dog servers all do this.
Best of luck!