Just an idea: you could adopt an idea from the Sub7Server Trojan, and build something on top of IRC — but of course not built on top of a trojan/zombie!

See the article "The Attacks on GRC.COM", in particular the bottom quarter of the article, on how it might work. Have an IRC client running on every machine, connect to a central IRC server, and you can send commands over that IRC channel, and have every client run the test, and report back over the channel.

There's no reason why an idea that's so easily abused for evil purposes, couldn't be put to good use.