Experimenting with idea of adding simple 3d axis lines (intersecting with scene geometry, to better visualize object's whereabouts in scene) dynamically to origin of any GameObject currently selected. The way I imagine it, it will run automatically on Unity startup and work in the background, without need to have custom EditorWindow displayed or manually attach scripts to GameObjects. Only requirement would be to put plugin scripts or dll in Asset folder.
For now, it works in sync with editor's Pivot/Center and Local/Global settings, positioning itself in same point as default gizmo.
Unity Forum thread: Unity editor - 3D geometry intersecting gizmo axis