I only use an expression pedal. This brings me to question I wanted to post here: I play my Rev2 and another keyboad in a live setting. My right foot controls the sustain of the other keyboard (and occasionally the sustain of the Rev2). My left foot controls 2 Yamaha FC7 expression pedals, which is actually unfortunate, because often, I want to dynamically change the volume or expression of both keyboard simultaneously or in the opposite direction.
Now, I have been crafting a number of cardboard prototypes of a two-way pedal with the volume of one keyboard in one (say, Y-) direction and the the volume of the other keyboard in the other (say, X-) direction. This design allows me to do exactly what I need. I searched a lot on the web, but such a thing does not exist. (there is one where you have a normal pedal with a little turn-table on top to give you a second axis; less ergonomic in my opinion).
So, my question is: I have been planning to invest some money in having a technician create a working proto-type. If some of you indicate that they are interested in spending, say, 250 dollars on such a pedal (given that it works well), I would be more tempted to finally push this idea through and invest a bit. (I don't aim to do this commercially, but making ten of these units will certainly be more efficient then only one).