The Rocktron All Access is able to show the On/Off status of the effect blocks, directly after a preset change. Of course, you'll need to connect both MIDI In and Out of the G-Major, as the unit transmits the On/Off information to the board upon preset change. Other pedals, i.e. ART X-15 will also do the job. The DMC Ground Control and Ground Control Pro achieves the same result, but in a slightly different way. It remembers all the block settings itself, so only a single MIDI connection will be necessary. Click here
to see an example on how to set up the Ground Control Pro. Lexicon MPX-R1 uses other MIDI (sys-ex) messages and cannot show the status.