I recently invented and built a push stick for inline skating (and maybe skateboarding). Some have already been built, but mine is (probably) the first ultralight version that uses an automatic gripping technique instead of static weight to hold the wheel against the ground. Weighing only 6.5 pounds, when not in use it can be easily carried instead of towed.
If you build stuff and can do light metalworking, it is easy to make.
Parts...
... DeWalt DW960 right-angle cordless drill
... an aluminum pole/tube, about 4 feet
... a 125 mm Razor scooter wheel
... a battery holder and speed controller (mine taken from another DeWalt cordless drill)
... ten inch aluminum flat bar
Construction... The right angle drill goes on one end of the aluminum tube, and the battery holder and the speed controller goes on the other end. That's about it. The aluminum flat bar is bent into an L shape and stuck on the aluminum tube with hose clamps. The least easy part is grinding/shaping the chuck to hold the scooter wheel. It can be made so that the wheel is held very closely to the large bearing part of the right angle gear. That was an easy method, but there are alternatives to mounting the wheel. Like doing away with the chuck and using the arbor with a bearing on the opposite side of the wheel, and adding a small aluminum flat bar fork. I'm not sure how long the right angle gear will hold up to the bending force of my current design, time will tell.
Auto grip, how it works... As the push stick pushes, the L shaped aluminum flat bar that is stuck on the aluminum tube presses against your back thigh. As the push stick wheel rolls in closer to your body, the counterforce of your body forces the wheel into the ground and provides traction. It is like a wedge.
It takes some skill to use, but I am no spring chicken and it's easy. Using the DeWalt 18 V right angle drill, the top speed is only somewhere between 10 and 20 mph. But it is surprisingly powerful, enough to push 160 pounds on inline skates up slight hills. Using DeWalt XRP batteries, taking one spare battery is more than enough for my needs. Individual needs will vary radically.
For reference, here is an example of a push stick that uses a handlebar.
It is loud and bulky using a gasoline engine, but it is powerful and fast. Notice the user in the video occasionally pushes with his legs as he is rocketing along the ground. The pushing is just ridiculous, it is simply to please the macho crowd who think that you must push in order to be a real skater. Propelled skating is a riot, and pushing has nothing to do with enjoying it.
One recreational use here for my Motail (motorized tail) will be on a smooth and huge sloped parking lot in the neighborhood. I zoom around and down, and on the final turn, I put the push stick down and effortlessly zoom back up the hill for another go at it.
Hopefully the weight can be reduced from 6.5 to maybe 5 pounds, without sacrificing any performance. Using a lithium-ion battery (of course), a thinner wall aluminum tube (currently 1/16"), and other minor changes.
Pics on my page.