Being a fun novelty accessory for one of the most acclaimed episodes in one of the most popular video game series ever, while also being an excellent pedometer on its own merit, it is no surprise that the Pokéwalker has received a fair amount of attention.
Considering the Pokémon community also includes a large game modding scene, it is no wonder either that some people wanted to discover its full potential; however most efforts (including a fairly recent and promising one on GBATemp) were, if not unconclusive, at least leaving more to be desired.
Not anymore: as of yesterday, Russian hardware hacker Dmitry Grinberg (who just signed up to GBATemp as @dmitrygr ) published his research, which can be summarized as follows:
- As somewhat previously known, the 'walker contains a generic program, that is customized with data from the DS game on both initial setup and the start of every walking session;
- Game Freak's average code quality being a known meme, the ROM ended up dumpable in a way vaguely reminescent of the GBA bios (taking advantage of an output function without sane range checks) and was shown as containing some questionably inefficient code;
- All text is a prerendered image (which combined with the first fact, still fits easily in the 64 kB flash)
- The data flow between DS and Pokéwalker has been documented, as has direct communication between two units (allowing for replicas and dedicated cheating devices);
- In fact, a Palm OS app was developed to allow anyone in possession of a compatible (and currently inexpensive) PDA to independently verify the claims;
- And finally, unused functions, likely for event distribution purposes, were discovered.
Source: Dmitry Grinberg via YCombinator Hacker News