Exactly the sort of thing I'm looking for. I was looking at the different players they have ported Roxkbox to over the past week since I'm in the market for a player.

At the moment it's looking like an iPod video but the Toshiba Gigabeat S model coming out looks pretty nice. The Gigabeat models are prime for hacking with a 300 or 400MHz ARM core and everything done in software. The processor and most chips are also quite well specified making it easier. The older ones (F and X models) run linux. I think the new S model is running some sort of Microsoft player though.