Unless you put the camera for the video feed on the front of your machine preferably in line with how you look at your machine it would be very hard to use. There would also be a considerable learning to curve to learn to look at the feed and use your hands on the machine below. I would also be concerned about the reliability of the video feed (we all know how tricky tech stuff can be) and as someone stated there could be delays or even pauses. Another concern would be how sharp a pic you would get. If you don't have a very sharp picture, it's not going to be usable.
My husband has used a Go Pro video camera but not for a live feed. I really can't remember how good the picture was.