I was doing some commercial group photography work using a Nikon tethered to a PC but it was a long time ago and I don't remember the software. The problem I found was the subjects kept trying to walk between me and the laptop.

For own own use (Canon) I simply connect the video cable to the camera and use an RCA extension lead to plug into the video terminal of a TV. I found this was very helpful when working with models as they could see the results virtually immediately and alter their pose to suit.