I don't know who makes it, but I have seen a power rack type system where the bar was attached to two cables on each side. You loaded the bar with regular weights. Unlike a smith machine where the bar travels up and down a fixed path, the cables allowed the bar to travel nearly everywhere. You could do any exercise with it, squats, deadlifts, bentover rows, bicep curls, etc.. what made it neat was that there was some kind of sensor in the bar and as soon as you raised your fingers from the bar it automatically locked in place, no matter where it was.
It looked awesome as a great way to train to failure by yourself with no worries about whether or not you can rerack the bar at the end of the set.