Maybe it would be more effective just to hire more border patrol agents, and improve the electronic surveillance. If Trump builds an "electronic wall" -- and it's effective -- he can count that as having delivered on his promise.
Perhaps more important than the wall itself, though, is to stop the acceptance of illegal aliens once they get inside. If they know they'll be sent back, they'll quit coming. (Except for terrorists, of course, who have no intentions of staying -- the ones backed by sophisticated organizations will still be able to come in by plane or boat, as with illegal drugs. With borders as long as ours, there's no practical way to wall ourselves off from everything. We can, though, stop the mass influx of illegal aliens.)
I have said all along....we don’t need a wall. What we need is someone with the huevos to force the enforcement of current laws. We already have laws in place to stop all this crap. They’re not enforced and the law enforcers are actually facilitating the illegals. If all that stopped the illegals here would go home or be deported eventually as they came into contact with government officials and the rest would stop coming.