GBAtemp member t377y000 has released a new homebrew for the DS/DSi. This Sonic fan-game is still a tech demo at this point, but includes animated models, physics, and basic custom collision. Join the on-going discussion linked below, and also be sure to visit the project's page for more information about this work-in-progress game.
QUOTE: Change Log 12/17/11•made Major changes to & cleaned the code.