Oh my, Rust vs JS. It's almost guaranteed there will be more comments about that than the actual treatment.

That's awesome that you created something free. You might want to add a standard license to your disclaimer for better liability protection (something that already stands up in case law).

Do you have any verification or adjustment mechanism to ensure the correct frequency across hardware variations? I assume this would be hard to do, but would be interesting if you were able to have something like that.