For the OP's benefit, you don't have to have a Scanmaster running with Powerlogger, BUT....... It' makes life so much easier when you're just out driving around and don't want to have to be messing with a laptop. It' provides nice visual cues. Scanmaster ver. 2.2 runs with the Powerlogger, Scanmaster ver. 2.1 is run independent from powerlogger, but has a slower display.
Hope that answers your question.