i've got peavey 1600 slider boxes and doepfer regelwerks. both have on/off contact switches in addition to sliders. i haven't seen a control surface that is 'just' on/off switches. most people would not want this since they also need the CC controls of the sliders.
btw, i've got the 360 system, ensoniq and jlcooper midi patchbays and i don't think you can use them to send the on/off midi messages. maybe i'm missing something.
btw2, i looked at the b*er control surfaces. i've heard from others that the precision o/t rotary knobs is not too good. the construction is what you expect from uli & company. caveat emptor...