thanks curt, found an air switch here: http://www.homeportfolio.com/catalog/Listing.jhtml?catId=483&avId=13970

always embarrassing to find something i haven't dealt with before. let me see if i understand ---- it's just a push button switch that's in some kind of receptacle housing with a pigtail on it that you plug into any receptacle? then you plug the disposer into this receptacle-housing air-switch-box, and it has another receptacle to plug the instant h.w. into?

thought about the 3-way idea, but it sounded too easy --- thought it should be harder than that [Linked Image]

i didn't want to run another circuit inside the walls or underfloor, so this sounds like the trick