Cable robots have some pretty neat abilities, but we don't see them everywhere in our daily lives. Some of pitfalls are that large work areas require high angles in order to keep the cable tensions low enough. For example if you wanted to cover the size of a football field, then you need a pretty tall tower on each corner to allow for high enough cable angles. 

That brings me to the concept of using them underwater.....

There are numerous articles out there about coral reefs that are dying or already dead, we have invasive species of weeds that infiltrate our fresh water lakes (for example Eurasian mil foil) , and we have large dead zones in our oceans (Gulf of Mexico, Mississippi delta). Underwater applications can use buoyancy to offset payload weight, thus don't require such high angles. The advantage of the cable robot is then you have solid idea of where it is at, (underwater positioning is not trivial, we are spoiled by GPS on land), and the actuators can remain above the water line for service. 

Maybe we see cable robots in the future farming and creating coral reefs. Maybe they identify and chemically treat invasive specifies in our lakes. Maybe they create life in dead zones by seeding tolerant lifeforms in lifeless areas.

They allow the ability to observe and to perform action.

 I just wanted to throw this out there to see if it spurs any additional outside of the box ideas. Looking for comments.....