What would harnessing of gravitational waves look like? We have harnessed and learned to generate and control sound waves, light waves, water waves, and electromagnetic waves in general.  What would be needed for science to be able to generate and use gravitational waves in the same way? What would be the outcome?
The mass of fundamental particles, like the proton or electron is very very small in comparison to the charge. This means that the motion of electrons in atoms can produce significant amounts of high frequency electromagnetic radiation. 

Quantum effects stop electrons from falling into the protons they orbit. 

To produce and control gravitational radiation in significant amounts you would need something very small, but very massive: a microscopic pair of black holes. 

Such things would be rather hard to manage. In short it is beyond any conceivable current or future technology.