And ‘every’ Mac developer thinks people will want to run their tool all the time.

For this kind of read-only tool, I doubt that’s the case. A regular application probably serves most users better.

Also, if you want users to have the option of permanently displaying this kind of info, a desktop widget (https://developer.apple.com/documentation/widgetkit) may be a better option than a menu bar item.

Exactly, this should just be a regular app with an optional menu bar option for those who want to switch it on.

I like this idea.