Far short of a proper review, however I have scanned the code. Bear in mind this was a purely personal project, never intended to see the light of day and initially just done to create a small but operable chunk of dbus/blueZ glue code for another project.

I have no doubt that a C developer with sufficient knowledge of dBus, bluetooth, the HRM profile and linux could have written the C code in a day. Adding the HTTP server again would be easy if the developer also had experience of that (n.b. there was a minor compiler error when I tried it on another system due to a slightly different version of libmicrohttpd). Adding the API would be straighforward (but tedious) and similiarly the web page (the web page was an one-shot after Claude wrote the API, vis. "Create a web page to display a real time plot with history using the API").

So overall I'd answer that that human developers would could have pulled that off in a day are few and far between (and likely to cost a lot more than $25 plus a day of my time).

And do I think the code is good enough? Yes, more than good enough. I could take it and run with it, against that because it ended up 100% AI-generated I feel a bit like leaving it as a monument to "pure AI".

After all, I never intended to release it - it was this thread that made my throw it up on Github as an example for the OP.