Sandisk is using Open Source as a weapon to fight against Apple iPod. From this article they plan to use Rockbox which is an open source firmware for music player. Rockbox can also be use dto replace the original firmware of many of the popular MP3 players to enhance the features.
Support for over ten Sound Codecs, including OGG and FLAC
Gapless playback DONE (with lame -nogap)
5-band fully-parametric equalizer, and crossfeed
High-resolution volume control, 64-100 levels (model-dependent)
Abilty to create your own themes or use user-uploaded ones
Advanced crossfading
ReplayGain support (volume normalization
JPEG image and text-file viewing
Doom – The popular game!
Real Time Clock (RTC)
Customizable ID3 Tag Database
Unicode support
Advanced On-The-Go playlist creation
Multilingual Interface – 30 supported languages and counting
Optional fully voice-driven interface
Many plugins – games, apps, and demos
Open Source, so Rockbox is constantly improved