Ultrasonic sound based mosquito repellent were all fad in early 2000s and there even computer programs for that but unfortunately they do absolutely nothing to repel mosquitos - https://www.bbc.com/news/magazine-20669080 .
There has been no revolutionary discovery for a safe, affordable, efficient mosquito control and hence the need gap. But there has been breakthroughs w.r.t medications and vaccines for diseases caused by mosquitos as a vector as I've mentioned in another comment.