I'm not certain that the Xtreme Mac's MicroMemo will replace tiny voice recorders, but it might be a start. I wasn't certain how long I could record, but I'm guessing it would be as long as my iPod memory would allow.
Not only did the MicroMemo attach very easily to my iPod, all I had to do was switch to Voice memos to get it working right away. I even tried it out in the library, and my voice was preserved even as a whisper. I definitely liked the flexible microphone which can detach for other forms of microphones.
XtremeMac has the MicroMemo available now on their site for $59.95.
Via Product Page