This might be a bit niche, but it would definitely work where I live.
Towns like Houtbay, South Africa that is famous for their horse farms in and around the town are spoilt with magical scenes like the photo above. Yet, not all residents are really happy about the number of horses in town. They hold up traffic, aggravate dogs, but the most irritating of all is the amount of excrement all over the streets.
Unlike domestic animals, horses can not be trained to go to certain locations. They simply do it as they are walking. Looking at the size of a horse I'm sure you can also imagine how much waste is produced.
There are dozens of riding horses in Houtbay and it's a small town. These horses need to be exercised every day and they tend to excrete more than once on a trip. So in the summer months, when it's not raining, the amount of manure on the streets really is becoming a problem.
Currently, it's just left for nature to take care of, which doesn't take too long. Wind, rain and traffic tends to make a pile disappear within a couple of days, but by the time one is gone, there are two more to replace it.
My idea is for a service, funded by the different stables and riders in town, that simply follows the riders' routes and cleans up the mess. If a stable pays for the service, they can receive badges for their horses and riders to indicate that they are contributing towards the cleanup, which could do wonders for their relationship with the rest of the residents in town. Whereas any stable or rider that refuses to contribute will look horrible, as it would appear that they do not care about the mess they make.
All that would be needed to run this venture would be a truck, a shovel and a broom. Receiving a subscription for each of the many horses in town could turn this into a very profitable undertaking.