Since 2015, President Donald Trump has promised to build a "big, beautiful wall" along the 1,950-mile US border with Mexico: a 20- to 30-foot high concrete wall/steel fence he says will stem illegal immigration, keep out illicit drugs and stop terrorists from entering the country.
On Wednesday, House Democrats unveiled a new border security plan that contains no money for physical barriers along the southern US border.
"We cannot focus on archaic solutions in order to address this very modern problem.
Smart wall systems could comprise technologies ranging from infrared and laser-enhanced cameras, drones, sensors and radar to artificial intelligence.
But these approaches could too easily violate our privacy, security and civil liberties, according to tech companies and the American Civil Liberties Union.
The ACLU described security technologies as "ineffective" and warned that "programs intended for border security purposes have had a tendency to expand toward the rest of the country."