[Musicians] Anyone know of a real-time tempo (BPM) detector for Mac?

[jim saxe]

Folks,

Do any of you know of a program will run on a MacBook (under
OS X), listen to music through the built-in microphone, and
automatically detect and display the tempo in beats per minute
(of course occasionally updating the displayed number if the
music speeds up or slows down)?

Please note the specifics of my question and don't tell me that
I ought to be asking about an app that will run on, say, a phone
or tablet under iOS or Android.  If you can recommend something
that runs on a MacBook with OS X and you happen to mention that
there are also iOS or Android or Windows versions of the same
product, that's fine.  But I mainly want something for a MacBook.

Similarly, if whatever product you mention is also able to do
batch processing and produce tempo profiles from MP3 files,
WAV files, iTunes folders, URLs of YouTube videos, or whatever,
that would be nice to know, but I'm mainly interested in something
that can detect and display tempo by listening in real time (and
without needing the user to tap along with the beat).  I'd also
be interested in knowing if the program could write updates of
the current tempo to a place where they could periodically be
read by some other process, such as a shell script, Python script,
Java or C program, etc.

Thanks.

--Jim