Teensymon v0.3.3 can be found in the Teensymon open directory.

VERSION HISTORY
---------------

v0.3.3 (2011-02-13)

    Minor change as requested by rsatrioadi.
    
      Changed: After hiding Teensymon for 5 seconds, the reappearing of the
          display no longer forces window focus upon itself. It now remains
          with whatever window has gotten focused since.

I dug into the bowels of my harddrive and found the release you were looking for.

Caveat: I have no clue how well it works on modern systems. It's literally been a decade since I wrote that super minimalist-tool to work well enough even on crappy laptops of that era.