Yeah, I guess NoteCalc will be useful to many people, it's just that I'm noticing the sad lack of utilization of LuaTex (probably because people don't know it exists and exposes the power of TeX through Lua).

The targets of NoteCalc vs. the tool I'm proposing would be somewhat different, too, because LuaTex outputs primarily to PDF, and I don't know if it can produce HTML.