The sale of devices claimed to improve a consumer's hearing was so much the province of charlatans that shortly after Congress enacted the federal medical device laws in 1976 hearing aids became one of the few medical devices subject to device-specific FDA marketing and labeling regulations. (Go here to view FDA's hearing aid home page.) Moreover, the need for consumer regulation was deemed so great that, nearly alone among medical devices, the federal government allowed the states to regulate hearing aids alongside the FDA. See 21 C.F.R. 808.53-.101.
But hearing loss is a serious health problem. Recent research shows that by age 70 almost 2 of 3 Americans will have significant hearing loss. The numbers soar to 4 out of 5 by age 85. Today's Washington Post has a series of interesting articles about what appear to be significant (but costly) advances in hearing aid technology. Go here, here, and here.