I found a (I think it was a motorola) cell phone hands free mike that had an eariece that (for lack of a better description) resemble the secret service style that fits into the outer portion of the ear......I have not yet had the thing fall out.
Something that would fit in the outer ear is what I vaguely had in mind. There's
thisfrom C. Crane that Arney mentioned. Interesting, a little wierd, but interesting. At least it can't just fall out/off.