I know that the software that came with my Canon's, any one of them I've had over the years, had software included that would allow you to shoot teathered.
I only tried it one time at a studio shoot and had my brother on the lap top with the guy I was shooting the products for. They sat in the other room and would tell me whether I was getting what they were looking for. If I was to do more studio work, I'd probably buy the wireless piece that allows you to transfer files to the cpu or hard drive without being tethered.
But all adds to the ever growing wish list