As we grow older, things stop working as well as they may have when we were younger; hearing and vision losses can be particularly frustrating because of our overwhelming reliance on those senses.
The hearing aid seems like a simple idea, but one that can be quite complex in practice. The generally accepted task of the hearing aid is to clarify vocal information, so that the wearer is not always having to ask their fellows to repeat themselves every few minutes.
As far as the existing tech and where it may be going, here is a good, short video from Leo LaPorte (The Tech Guy!) as a caller poses the question after realizing that he may indeed need to start using such a device. Leo makes a couple of interesting observations about hearing aids in general, and some forthcoming technology in particular.