Right now there's only two other pedals that we know of the Empress Pedals that can interface with the Empress Midibox:

Chase Bliss Warped Vinyl (chorus pedal) - you need a special cable for it to work

Chase Bliss Wombtone (phaser pedal) - you need a special cable for it to work

Hopefully we can get some other manufacturers to make their stuff compatible with the Midibox. Please bug them for us :-)