At some point a couple of years ago, I was into video and wanted a way to shoot smooth footage while walking / skating / going up stairs and what not. To do that, I constructed a stabilizer, following a standard Glidecam design. It involves a 3 axis pivot, and a stem with camera mount at the top and balanced weights at both ends.
I built mine around an M8 screw rod, with skate bearings and PVC pipes held together by nylon locking nuts. It works really well, even not properly balanced. The video below is casual walking (not trying to be smooth).
Such bulky and reasonably weighty construction however is not very convenient, nor pleasurable to operate, given the alternatives such as Feiyu G3 motorized gimbal. Ofcourse, for smaller cameras like the GoPro or a mobile phone.