Non rockbox, non easily swappable battery (though it uses a rectangular cell with a JST connector), looks like an early ipod, no speaker(?), costs $249? Um no.

Non rockbox, non easily swappable battery (though it uses a rectangular cell with a JST connector), looks like an early ipod, no speaker(?), costs $249? Um no. There are still plenty of Sandisk and other players around that can run Rockbox. I still have a Cowon D2 that had a Rockbox port that apparently wasn't really complete. Its main drawback as I saw it was not supporting SDXC (i.e. largest supported SD card was 32GB) but in retrospect that's not so bad. I don't remember whether the Rockbox port supported the SD card at all. The player had 16GB of internal flash and a full sized SD slot. It had an excellent DAC and plenty of drive power in its headphone amp, while still having around 50 hours of play time on its 1600mah(?) lipo cell. Replacing the cell with a phone battery of the era wasn't too difficult. It was a great player and would have been even better if they had opened up the hardware docs enough to get Rockbox completely working. The player I wished for in the early 2000s had an SD slot, had an AM/FM receiver, and ran on an AA cell. Today, realistically, it should also have bluetooth. Depending on its size, maybe it could use an 18650. On rockbox.org there is a forum thread about porting rockbox to Android and apparently there are significant technical obstacles to doing that. I don't know what the obstacles are. I don't offhand know of Android music player apps that I really like, but there are some usable ones. And phone hardware is good enough for this purpose that the whole induestry of dedicated audio players is now close to wiped out.