I know with smart strings, there may not be a lot of interest in viewing the DMX transmission. However, for those on Mac OS X 10.7 (lion), with FTDI 1.0.4 D2xxx drivers and a ChronoVu USB Logic Analyzer, I have some software that will show you a high level DMX frame context (if it detects any), and then lets you drive down into the frame with another window so you can see the actual data values (and logic traces). This view is always available, even if no DMX frame is detected (it will just show a standard logic trace, without channel/frame information).
I don't know how many people tinker with their own hardware projects, and I know those that have Mac/OS X Lion/ChronoVu are limited. But if you need something like this,let me know.