I'm looking for something that helps me mount my camera on my guitar headstock for some close-up fretboard recording
Here's a video for ref. http://www.youtube.com/watch?v=kqsuet6lMzE

Even better if there is a camera made just for this. I'd hate to have a heavy one attached on one end.
You could use a webcam, or a small digital camera, and attach it with tape or several velcro straps.

I've seen a camera which has a separate lens (well, not just the lens, the optical receiver part) that you can connect. Maybe he used one of those.