A Mobile Garden bed
I've always had this idea for a mobile raised bed garden that could be wheeled into some "waste" area (empty lots or easement strips) in full sun, and could easily moved around. Basically a container garden in a wagon of some sort.
This is probably inspired by a large amount of vacant acreage near me. Originally it was a corporate site, but the building was razed after it was sold to some developer who was going to put homes in, but then they went bankrupt and there were some kind of lawsuits going on from the investors. Nothing but weeds and grass that some company comes and mows down occasionally. Seems so wasteful for it to sit for years. Especially in the city where that kind of space is rare.
Anyway the more complex versions of it I envisioned could even have a built in water tank for watering. I'd think it would be useful for someone that may want to have the ability to easily move the garden around to keep it in full sun throughout the day.