Is there such a thing?

I have a project at the end of the month to video, and I would like to run two cameras and switch on the fly. What is the easiest and most affordable way to accomplish this?
Are there any software switchers out there that would take two firewire feeds into my laptop and allow me to switch them on fly direct to an external hard drive? What about audio? Is it possible to have two video sources, but have the audio coming from just one camera for the entire production?
I really do not want to have to edit this after the fact this year.

Thanks

See the following thread: http://www.dvinfo.net/conf/showthread.php?t=56413