For a shoot (where I was running backwards through the woods) I made a simple steadicam which works very well.
A steadicam is basically a pendulum which adds inertia to the camera movement. It's suspended directly underneath the camera, here just with my hand and arm. The two exercise weights at the bottom add the inertia. The longer the boom and the heavier the weights the smoother is the movement. Because the DSLR is pretty light the weights at the bottom need not to be that heavy to pull the camera in a vertical position. What is trickier is the rotational movement of the camera which is prevented by having two weights sideways on a metal bar. Ideally, the rotation could be even more dampened by a soft suspension. It's not that optimal to hold the pendulum directly with your hands. It would have been better to have a handle sideways but I never managed to build that. As long as the camera is held pretty loose in your hand also the rotational movement is pretty smooth.
I use 1kg of exercise weights but could add a second set (after more time in the gym!). These are from a set of exercise weights I got from Argos. The aluminium sheet at the bottom and the screws are from B&Q. The tripod was just a cheap still camera tripod which conveniently had this quick release mechanism attached to it which lies quite nicely on my hand and acts as a bearing: