You don't actually need a camera. Currently I am streaming only my live audio feed to ustream via a headless Windows box. All I do plug in a cord (
http://www.bhphotovideo.com/c/product/253265-REG/Sennheiser_CL1_CL1_Mini_to_Mini.html) into the scanner and the other into the Windows box's sound card on the back of the tower. When you open up the ustream broadcast console, it will ask for permission to use the video and audio feeds. Click "allow." Since you won't have a video feed, it will automatically just use the audio feed only. So, in short, no, you don't need a webcam. For an example, you can check out
www.iowascanstream.com.
My stream is currently using a spare Pro-2052, but it will be upgraded to a BCT-15 when I upgrade my mobile setup. When that happens, I will be using the same setup for the audio feed, but I will be using bcTool's remote control feature, using something like WebcamMax (
http://www.webcammax.com/) to capture the remote control screen to show listeners what talkgroup is currently broadcasting. When using WebcamMax, ustream will recognize it as a "camera." But in no way is it necessary to use a webcam in order to broadcast on ustream.