Actually, I don’t beleive a wall will work unless there are boots on the ground to defend it. And if there are boots on the ground in remote areas...why build a fence? Perhaps you are not familiar with the southern border and the terrain in the area..
No sarcasm. :)
In military terms the wall is a force multiplier. Nobody said an unmanned wall. It takes an order of magnitude less troops/agents to patrol a wall. The wall is MORE important in the remote areas because that is where supporting troops is the most difficult. Walls are non political and are on duty 7/24/365.