Need camcorder or digital camera with optical zoom to function as webcam via USB

I'm searching for a camera solution that will allow me to stream live events (probably via ustream) with a device that has an optical zoom and tripod mount.  Any device that shows up as a webcam should work.  So I need either:
1. Webcam with an optical zoom
2. Camcorder or pocket camcorder that has webcam function
3. Digital camera that has a webcam function

I'd actually prefer a digital camera or camcorder to a true webcam in order to have an LCD screen on the unit on the tripod so it can be used some distance from the recording PC doing the streaming.

Requirements:
1. Must stream via USB, not firewire
2. 5X optical zoom or better - zoom must function when in "webcam" mode
3. Tripod mountable (without blocking access to USB port)
4. Works with Windows (preferably Windows 7)

Would be nice to have:
1. Function as stand-alone camcorder saving to memory card
2. External mic jack (for use when using as stand-alone camcorder)

Budget: $300

One of the Sanyo Xacti models had all the features except that the USB connection is via a base station, so can't be used at same time as tripod mount.  Another one of their models didn't need the base, but manual said the zoom can't be used when hooked up as a PC camera.  Sony Bloggie looks nice, but no webcam function.  FlipVideo devices don't have optical zoom.