For a editor VP solution see Custom show flag

Component Visualizer

There is a struct called FComponentVisualizer that seems to be used to draw/debug whatever you want for a specific component class.

See FConstraintComponentVisualizer::DrawVisualization and FComponentVisualizersModule::StartupModule for an example.

See zomg’s post for the base setup.

About GUnrealEd in StartupModule

As I found here GUnrealEd is null in StartupModule if you are loading it to early. Load your module at PostEngineInit phase to correct that.

More details about it (with an example on Unity box collider 6 faces maker) here