I've been using the Samsung Yepp! 128MB pendant MP3 player with the Etys 4P with excellent results. Around two hours of music after that you do need to reload.
Battery life is about 4-5 hours on a single AAA. Software is so-so, recommend using a separate ripper (MusicMatch) and downloading the Yepp! Explorer from the Samsung web site.
If I were buying today I'd take a good look at some of the USB thumb drive/MP3 players. Easier to work with - no special software and no cable to carry.
Cheers,
Jeff
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"When the going gets weird, the weird turn pro"... HST