That worked right out of the box !
So it seems that if you only need the output from the tiny you would choose KnockBang, and if you need to also send something to the tiny you would use RelaySerial ?
That's what I do. Knock-Bang is smaller, faster, more reliable, uses a pin already connected to the programmer, and consumes almost zero CPU time if the programmer is not connected. For simple debugging it is a great choice.
Another observation in the test script you use
Debug.begin( 250000 );
But you have to set the serial monitor to 19200 (I mean usually they should be the same) ?
Sort of. My ultimate goal is to provide three Tiny Debuggers: Serial, Knock-Bang, and Null. The parameter (the "250000") will eventually be the baud rate for Serial. For the other two debuggers the parameter is ignored. You can put what you'd like in there but 19200 is certainly a better choice.