Can you recommend a high-def webcam for OS-X?
I would think finding a true "High Def" webcam would be hard to find. Most webcams that I see that shoot in a resolution over 480i do so using software or scaling.
Plus the connection speeds you would need to be transmitting at that rate would be rather large. (and theres no guarantee that the video quality wouldn't be reduced automatically to speed up transmission)
As much as it shocks everyone one of the best and cheapest web cams I have used is the Xbox Live Vision Camera from Microsoft. For $40 you cant beat the image quality. I have bought 2 of them so far.