"Broadcast" can mean a lot of things. Are you testing for the ability to run some particular broadcasting software, like VidBlaster or Flash Media Live Encoder?... or some simple Web cam program?
At the very least you will need to use some server side scripting to react with the viewers machine.
Perhaps you could incorporate something like BelArc Advisor to do the audit, save the results as a web page and then report back to you.
But speaking as a longtime producer of both recorded and live Internet video, I'd be at least as concerned about the client's Internet connection speed as I would about the client's machine specs if you are intending to do any Live video broadcasting.
A client could have the latest i7, 32GB RAM.... etc, etc on a DSL line and not be able to sustain a Live broadcast while another client could be on Windows XP, 512MB RAM on a 6Mb highspeed Internet connection and broadcast Live just fine.
Eye for Video