One of the bits of technology from the Stainless Steel Rat books which always sticks in my head is the ‘monocycle’ which made an appearance in the original 1957 story:
To someone of little imagination I suppose it would have been an awe-inspiring sight. At least five armed guards standing around the entrance, two more inside the truck as well as the driver and his assistant. As an added precaution there were three monocycles purring next to the curb, they would go with the truck as protection on the road. Oh, very impressive. I had to stifle a grin behind my cigarette when I thought about what was going to happen to those elaborate precautions.
They always sounded pretty cool to me, and Carlos Ezquerra drew them in the 2000ad comic adaptation which made them look even cooler.
Back in November 2003 Forbes.com posted a story about a concept for a monocycle, created by Quebec-based Bombardier Recreational Products, makers of ATVs, skidoos, and such. This was a concept for the kind of vehicle we might be riding in 2025.