At least two South Bay firms want to help President Donald Trump build a “great, great wall” along the southern border. Sunnyvale-based remote-sensing manufacturer Quanergy is one of several Bay Area companies to submit proposals for the unfunded $20 billion-plus barrier between the U.S. and Mexico. Landing the contract could potentially bring windfall profits for the immigrant-owned company, but could undermine business prospects in the politically liberal region it calls home. Two San Francisco County supervisors, Hillary Ronen and Aaron Peskin, introduced a law that would prevent that city from doing business with companies that apply for work on the wall—whether or not they win a contract. Oakland and Berkeley already passed measures to blacklist aspiring border wall contractors, while cities in other parts of the nation weigh similar measures. That’s to say nothing of the public backlash that would no doubt ensue, despite scores of border wall bidders being minority owned. Quanergy CEO Louay Eldada, who emigrated from Lebanon, has yet to return Fly’s request for comment. But in an interview with the San Francisco Chronicle, he defended his proposal as applying “Silicon Valley innovation to achieve the positive security goals without the negative repercussions.” Eldada told the Chronicle that he wants to use Quanergy’s signature laser sensor technology, known as lidar, or “light detection and ranging,” to monitor the southern border. The “smart fencing” would detect and analyze movement and transmit live visualizations to border agents. Eldada’s is one of many high-tech plans put forward by companies to bolster or replace a physical barrier. Mountain View’s Future Fibre Technologies, which specializes in fiber-optic security sensors, is also vying to work on Trump’s pet project. U.S. Customs and Border Protection officials, however, advised that technology alone would be insufficient.