Tony, the author for the GBA JPG Viewer, also works on a video codec to use with the GBA. There are allready 4 techdemos avaliable.

The Caimans video codec brings video on your Gameboy Advance(tm) , with a new fast algorithm designed to achieve high quality at low data rates and visually optimized for GBA’s lcd display. Youcan watch Caimans codec in action downloading the examples in this page. Please note that the demos povided refer to the actual beta version of the lib and use HUGE uncompressed PCM audio. Furthermore the caimans video codec is optimized for the REAL GBA display, even if you can see some noises and artifacts when playing demos with an emulator, the quality improves when using a real GBA. If you have a GBA flashcart I strongly suggest you to try a demo on the real hardware. Contact the author for further details

Thanks toLucifer Lovefor the news again!