Terrain Following Support

[Cyberpilot360]

Mission planner and Copter 3.4 now support terrain following in AUTO, Guided, RTL and Land modes, as many of you already probably know.
This is extremely helpful in terms of safety (making sure the copter doesn't crash on a hill during a mission or RTH). Furthermore it is a necessity for accurate surveys and mapping applications (making sure you always maintain ground alt.).
This feature can be put in use by utilizing the ground altitude data of the google maps provider.

Is Tower any close to supporting this feature?
I read @billbonney has done some work regarding it?