You know the tool, it's for keeping a video camera steady while you walk around. It has a cool smooth operating effect, and is responsible for making sure we all don't puke at every action movie.
The best ones are hooked directly to the body of the camera person, and the lightweight ones are hooked to a waist-belt that transfers the weight to your hips like a big backpack would. It takes the weight off your shoulders, and lets you keep your arms more free.
I need something like that for carrying my baby around for the hours (sometimes) that it takes to hand-rock my baby to sleep. I have an "Ergo" carrier, but it often squishes them a bit too much and they don't sleep well in it. I want it to be able to support my now 11 lb baby's weight and let me kind of jump walk around with it to give it some motion. I don't want it entirely steady, so some kind of pendulum system should be employed, or perhaps a heavy vibration motor installed.