The hearing aid world converges with the iPod world, and consumer electronics in general, as described in this article from the St. Paul Pioneer Press. The figure shows hearing aid earmolds attached to iPod earpieces, providing a comfortable and secure fit, reducing interfering sound from outside, and reducing leakage of low-frequency sound with the tighter fit. Small, low-power audio earpieces definitely have a market, and the possibilities here are interesting.
(Disclosure: I work for the company discussed in the article but am not working on the consumer technology described. I did that gig at Sound ID).