Most of it is already built and there are many forms of technology in place already, they just need to fill in the gaps and increase the technology. The amount of money is a drop bucket. If the average citizen had any idea where their money is going, daily; they would ******* their pants!
We have friends that have worked border security, law enforcement and FBI. Their opinion is that every deterrent helps. If they don't spend the money on the wall, they will pay it out to security(in various forms), anyway.
Most people talking about the wall really have no clue other than what they have read. And what they know is generally from people that agree with their point of view. I like that I have been able to talk to people who deal with the problem on the ground, day to day.
If walls don't work, why are all the politicians living in gated communities and have walls/fences/gates and guards for their own homes? Businesses? Government offices? Take them down and put up some cameras.