A Steadicam is a very simple principle that is very complex in execution. When Garret Brown came up with his concept of Steadicam, handheld photography was becoming widespread. The camera had finally gotten light enough to carry, and people were pushing the limits. Cameras were still pretty heavy though, and the only way to carry them for any length of time and get a properly controlled movement was to rest them on the shoulders of the operator. This imparted even the tiniest movement of the operator to the camera. The original Steadicam is actually the human arm. Think of carrying a cup of coffee. You walk, the coffee doesn't spill. You trip, and if you are skilled at carrying coffee, it still doesn't spill. In fact you can do some pretty radical running or dancing without spilling your coffee, because your arm protects the coffee from all the shock. Now take that same cup of coffee, put it on your shoulder and try to walk, turn, whatever. I'll wait a minute while you apply burn cream and change your shirt.

Movie cameras are still too heavy to operate off of a shoulder, and still require a steadicam to pull off that "steadicam" look. However digital cameras are not that heavy. It is totally possible to operate many of the newer hi-end electronic cameras with one hand. Your time would be better spent improving your operating than building a steadicam rig. Even if you had one, you'd still have to spend quite a lot of hours practicing. However, if you really need one, there are plenty of steadicam guys out there with new rigs and no reel. Check your local rental house and if you've got a serious project, you'll be able to find someone who will work on your project for free so he can build his reel.