To follow up on @patrix's answer, this Yahoo Answers post indicates that there isn't currently any app that will do it, even on a jailbroken device. This Stack Overflow post also indicates that there are no APIs to do this at the moment.
However, there are music editors like Houkusai (iTunes link). In its app description, it claims to:
- Import tracks from your iPod music library
However, it's likely to be overkill for what you're looking for, since it's meant to be a music editor and not as a track editor.
In summary, in a search for track/id3 editors, I've found only applications that will work on a computer, not on an iDevice.