The Phonofone II by Science and Sons is a prototype amplifier designed for your iPod:
Without the use of external power or batteries, the Phonofone inventively exploits the virtues of horn acoustics to boost the audio output of standard earphones to up to 55 decibels (or roughly the maximum volume of laptop speakers)
Upon connecting active earphones to the Phonofone their trebly buzzing is instantly and profoundly transformed into a warm, rich and resonant sound.