hachistep is an alpha Pokéwalker emulator core written in Rust. It aims to be accurate enough to the retail hardware to facilitate custom firmware development, and performant/efficient enough for everyday use.
A cross-platform GPUI frontend can be downloaded from Releases.
There's also hachiware, hachistep's sister project which exists for end to end benchmarking, testing, evaluation, etc.
Why is it called hachistep?
Because the Pokéwalker's chip uses the H8 architecture. "Hachi" is Japanese for 8. Thus, hachistep.