So those suggesting OCAS / FLARM are you suggesting installing the devices on every mountain as well? Many more CFITs due to mountains than due to buildings!
I think most people that support technical approaches to the problem, want to use it on obstacles that are hard to see, masts, wind turbines, powerlines, etc, that is things that break away from the terrain features in the area.
I have not seen anyone advocating use of such systems for avoidance of terrain/obstacles for IFR/IMC. For that there are better things available, such as EGPWS and TAWS.
When I fly in my plank (sorry
) VFR along a valley at say 800ft AGL, I might be several thounsand feet below safe IFR altitudes, but it might be great to get a last chance warning about the new spindly tv mast of the digital ground net some fool has placed half way up the valley side. (Terrain backdrop, and a b*tch to spot even in good light conditions)
I find the terrain features in my 695 a bit lacking with those kind of obstacles.