Gustavo appears to be looking for a solution that does not rely on FMS. Has anyone found a solution that would fit was he is looking for? I am also looking for a method to record webcam video and audio to a use's local file system. I have been looking into Flex and AIR, but I have yet to find something that can do the trick.
You can use the Flash Media Live Encoder to both stream Live video or as a simple recorder, by unselecting "Stream to FMS" and checking "Save to Disk"
It's free, works well... get it here:
There is also a section here in the Adobe Forums dedicated to the software if you need more info.