Starting with the iPhone 4S, Apple added an accessibility feature to optimize the function of the iPhone with hearing aids.[141] Apple released a program of Made for iPhone Hearing Aids.[142] These hearing aids deliver a power-efficient, high-quality digital audio experience and allow the user to manage the hearing aid right from the iPhone. Made for iPhone hearing aids also feature Live Listen. With Live Listen the iPhone acts as a remote microphone that sends sound to a Made for iPhone hearing aid.