By 'sound activated cold cathode tube' do you mean you want it to flash on and off to sound ? I suppose you could rip a microphone apart and wire it up to one of the button connectors, then find out what letter it sends. I've never used LCDC but i presume you could set an event triggered to that key...

If you mean to use Javascript or a Java applet, you'll probably have serious trouble with permissions for writing to the serial port. I know the earlier versions wouldn't even let you read/write files on the host machine altough I think this was changed. Anyone trying to use the site would probably ...