Rockbox Ports are now being developed for various digital audio players!
This isn't really possible with anything but WAV and maybe a few other formats, so its not going to happen.
I think probably the best you could do would be a plugin that decoded the file to disk, reversed it, and then let you play the reversed .wav file. If you want to work on that, I think it would be doable.
Page created in 0.071 seconds with 20 queries.